July itinerary by train

1. Very little chance of being completely stuck I would think. Something always works out.
2. Too many one nights
3. There is a type of ticket called Advance. They are limited in number and when they sell out at the cheapest price point, another limited number go on sale at a slightly higher price point. Then once they sell out the next tranche goes on sale, and so on. Other ticket types are Anytime and Off Peak - they are fixed price - never sell out and are the same price whether you buy six months ahead or on the day at the station.

I'm not convinced of Wednesday and Thursday.

Brighton to Weymouth is either via London (change stations) or coastwise via Portsmouth and Southampton. Either way it's a good half day travelling so not much time there.

And Weymouth to Plymouth is not that easy- you have to go inland via either Castle Cary or Westbury- another good half day of travelling.

Two nights in Brighton is only one day. I would add an extra night in Brighton, skip Weymouth, then go to Cornwall via London. When in Plymouth you want time for at least one of the boat trips and to visit the Barbican and harbour area- which isn't in your existing itinerary. Then get more time in Cornwall by flying back from Newquay to LGW.
That will be cheaper on TA air fare than open jaw.
It is also more resilient to train strikes as most of the itinerary could then be replaced with Nat Ex Coaches if needbe.
Once in Cornwall you have the good and cheap local bus services to replace/supplement trains, even if the frequent timetable recasting is becoming maddening. £5/day anywhere in Cornwall/£20 a week.
There is a Cornwall day rail rover "Cornwall Ranger"- see link below, but if going to Looe you must hop on the bus to Polperro- that bus also goes direct from Plymouth. Then bus Polperro to Liskeard station for your onward train to Penzance.
There is also an integrated bus and train day rover ticket- "Ride Cornwall"- https://www.gwr.com/your-tickets/choosing-your-ticket/rangers-and-rovers
Penzance to Falmouth is hourly direct bus via SMM. I have done Newquay to Penzance and Lands End return by bus in a day, but it's a bit rushed, a single trip is easy (one change at Truro, faster and far more frequent than train) then at least one night in Newquay before your flight home.
London to Weymouth and Weymouth to Plymouth book in advance. The rest is turn up and go.

On strike days there are always trains Brighton to London and London to Plymouth, but not west thereof, also London to Southampton (but not coastwise from Brighton to Southampton, and not Southampton to Weymouth).
Nat Ex would get you from Newquay to Bristol and Birmingham if you want to keep that route and be strike resilient as needed. By all means book trains but have coach as a standby.
On a Strike day a mixture of the Jurassic Coast service bus and the South West Falcon bus (an hourly long distance Bristol to Plymouth coach that runs 24 hours a day) would get you from Weymouth to Plymouth.

It seems to me that you really want to see the south-west of England. I see that you live in Palma, Italy. If that is so, you could well find flights from northern Italy direct to Bristol Airport which would be a much better option for you than Gatwick - and you could skip Brighton - which I do not rate highly. Easyjet and Ryan Air are the most likely contenders for flights to Bristol. Go to the following website and put in for FROM Bristol to Italy and select monthly view. Now see if any airports near Palma show up:> https://www.skyscanner.net

Bristol is on the main line to the south-west and also has a slower line with direct trains down to Weymouth.

This is Bristol Airport's destination page which details which airports have flights to Italy, and their operators.
https://www.bristolairport.co.uk/where-can-i-fly/explore-destinations/

Hi everyone and thank you!
Yes, I'm well aware there are flights to Bristol, but unfortunately not on the days I would need to catch the flight.
I think I'm going to skip Weymouth and I will focus on Brighton and/or Cornwall.
I looked at flying back from Newquay to Milan, but that's a bit too expensive. I'll see if I can find a solution. Maybe flying to London and catch another flight there.
Thanks for letting me know about the bus routes!

Hello again, I've decided to focus on the eastern side this time. I'll keep Cornwall for another trip.
I've come up with this plan, what do you think?

• 2 nights in Margate, on the last day I'll do the walk to Ramsgate.
  • 1 night in Ramsgate
  • train to Eastbourne and spend the night there. I plan to do the trail to Seaford. Yes, I know it's about 22km and no problem at all. I only have a small backpack and I'm used to walking a lot. :)
  • 2 nights in Seaford. I thought about staying here 3 nights, but I preferred this option instead of going back by bus after the trail.

If I can, I'll add another night to the itinerary.
Do you know if there's a weekly bus ticket (as the 20£ ticket in Cornwall) in case of train strikes?

Gigua,

The problem with a weekly ticket is that you start in Kent and then go to East Sussex. Also Cornwall is a trial county for integrating transport so that ticket is unique to Cornwall.
Margate/Ramsgate and Eastbourne buses are all run by Stagecoach. They have a South East 7 Day MegaRider ticket which costs £28.30, only available on a Smartcard which costs an extra £2.
Do not under estimate the bus journey from Margate to Eastbourne- there are multiple changes on a journey which takes over 6 hours, so a full day, if it had to be done.
Given your itinerary you may be better off paying local fares around Ramsgate and Margate and getting a paper South East Day Rider costing £8 for the epic transfer day. That would need careful thought.
Beyond Eastbourne to Seaford you are in Brighton and Hove buses territory.
They have a day ticket for £7 and single tickets between Eastbourne and Seaford are £3.70.
On a Strike Day you would bus to Brighton, then train Brighton to Gatwick/London.

@isn31c - Thanks for the info! I really appreciate it.
I'm choosing only accomodations with a free cancellation policy, so that in case of strikes (which are announced at least a few weeks before, if I'm correct) I can modify my itinerary accordingly.
I could happily spend 6 nights in the same place if I'm honest. We'll see what happens.