Train confusion question

There are a few East Deans in England. Which one are you staying in?

We are staying near the Seven Sisters, close to East Bourne

The way I would do this personally is to go Elizabeth Line to Farringdon then Thameslink direct to Brighton catching the 12X or 13X bus at the other end of its route at Brighton Railway station- 1 hour ride.
Buy from any train company- LNER is the easiest. You can buy as one ticket but the cheapest option is to pay contactless on the Elizabeth Line then buy a ticket Farringdon to Brighton. Pay the bus fare to the driver.
The other way is tube to Victoria then twice an hour train to Eastbourne but I believe you walk down the street from the station at Eastbourne for the bus. I think Brighton is the easier interchange.

Whichever route you choose, you need to pay for the bus separately on the bus, and then the whole train journey can be bought as one ticket, including the London changes by tube or Elizabeth line. So buy train a ticket from either Brighton or Eastbourne (whichever route you decide to take) to Bath Spa. That ticket will take you all the way.

I've just been looking at tickets. The cheapest tickets from Brighton (on a route which is only 15 minutes slower) are on a route avoiding London. Train Brighton to Fareham (near Portsmouth), train Fareham to Bath- every hour.

On that route fares from Brighton start at just £20 before railcard discounts.

This is such an easy route it beats the socks off via London- bus to Brighton station then a same platform change. Should have been obvious.
The second train is a Portsmouth to Cardiff train.

From East Dean - take the 12 Coaster bus westbound to Brighton station. Then take a train to Fareham where you change for GWR train for Bath. You will find this cheapest if you book in Advance & has been said above, the price can be as low as £20 even without a railcard. This is much cheaper and easier than going via London.

https://www.traintickets.com/?/ is one of the easier train booking websites to use > put in for Brighton > Bath and select ‘Advance Options’ and tick the box that says ‘Avoid London’. Search. (It will still show the dearer routes via London but also you will clearly see the much lower price route via Fareham). The GWR train at Fareham will be going to Cardiff.

I have gone to the website recommended to purchase tickets however the lower cost tickets say no longer available. Suggestions?

If you are travelling in August the Advance (cheaper) tickets are not yet released. They are only generally issued 12 weeks out.
As the first train is a Southern train their 12 week rule applies. GWR (who run the second train) now open 24 weeks out with exceptions. But the tickets simply don't sell out in the intervening weeks.

I was actually just using dates within the next 3 weeks to check how it works, so by August I have a clear understanding.

You should be seeing £32 for off peak trains next week on the direct route from Brighton (the next tier up) and £42.50 for via London.
The via London fare is also a good deal given that the Paddington to Bath fare is £40, and that the through ticket includes the tube/Elizabeth Line meaning that Brighton to London is effectively free.

And do I purchase a ticket for a train for Fareham from Brighton then one for Bath? Help again!

If you put in FROM Brighton TO Bath and have selected Advance Options and then ticked the box for Not via London - the fare you then see is for the whole journey from Brighton to Bath via the change of trains at Fareham.

If you would like to try that out and then come back here and tell us the fare you are seeing and also for how many people plus the date and if you have a Railcard or not - I am sure that someone will come back here and tell you whether or not that is correct prior to you actually going ahead and doing the deal.

You might want to allow a bit of leeway for time to wander around Brighton and in case the bus is delayed.

The train journey on this route does involve many stops so don’t expect a bullet train!

Success!! There are four of us the cost is $128 without the rail card. This is the first one I could find that travels through Fareham, other journeys had the route going through Reading. Thank you so very much!

On the traintickets.com site, I am not seeing fares for August yet - which means they are not yet loaded on the system. I have gone as far forward as July and am seeing fares as low as £20 per person = that would be £80 for the 4 of you. The fact that you could tick a box to say that you wished to avoid London brought up the cheaper route - which is also slightly faster than going via London - despite the slower trains.

Beware of currency conversion charges. Most Brits are aware that certain bank cards charge more for currency conversions than others.

If you are doing more journeys by train whilst in Britain, it might be worth you getting Railcard.

So as the journey to Bath is on 18 August (on checking back through previous posts) the cheap tickets should be released on 26 or 27 May.
Cheap tickets for the journey down from London should be released a day or two earlier but may be in very short supply due to the Airshow.

If they prove elusive a Southern Rail day save ticket may be the most cost effective option. For 4 people that costs £52, no further railcard discounts- https://www.southernrailway.com/tickets-and-payment-methods/daysave