Great Western Trains in England

There is a train roughly every two hours. It takes 5½ hours
As Emma says, all trains between Cornwall and London (and all local trains in Cornwall and Devon) are run by GWR, you have no choice. Website: https://www.gwr.com/

If you want the timetable in booklet form, it is here: https://www.gwr.com/~/media/gwr/pdfs/timetables/may-2017/gw1705,-d-,w01c,-d-,dl,-d-,513036,-d-,00,-d-,web,-d-,amended.pdf?la=en

I am not sure what further information you were looking for. Please ask.

It's a train. You sit on it and it takes you from London to Penzance. You don't exactly have a lot of choice in trains - it's not like there's 10 different companies plying the route.

I'm baffled by what could be "sketchy" about a train (incidentally in the UK, sketchy means approximate. I believe it means somehow fishy or unsafe in US English but I'm not quite sure.)

The food isn't great but you can bring your own. Sometimes some of the toilets block up but that just means walking another carriage to find one that works. The seats are perfectly comfortable even in Standard class - although I personally would spend up to £20 extra if I could find a cheap First Class ticket, just because there's a bit more room to walk up & down.

I've just had a look at the reviews - a lot of the one star reviews are from people complaining about overcrowding on the London to Swindon commuter line. Well, that's not going to affect you, especially if you pre-book your ticket and reserve a seat, as this isn't a commuter line.

Others complain about train delays/cancellations. This can be a fact of life - trains get cancelled if someone throws themselves on the line (I've been stuck on trains several times because of that) - and this particular train line runs along the seafront through Devon so can be subject to weather delays.

One person decided to give them a one-star review because they sat in the quiet carriage and kept hearing the "ping" of people's text messages.

People like to complain about trains. But generally they get you there.

You can on a few services enjoy the only proper dining service on a UK regular train from Plymouth onwards. You don't even need to book first class (although that may be advisable to book in advance). TripAdvisor very positive overall on that.

The sleeper is still running, and popular. Details here: https://www.gwr.com/plan-journey/journey-information/on-board/night-riviera-sleeper

Has anyone here taken this sleeper car? Or tried to book this sleeper online? I'm wondering if it's a good option to get to Penzance after arriving at Heathrow earlier in the day. I thought 2 adjoining singles would be good, but couldn't see a way to request this on the site.
Thanks for the link, Chris.

Dani, yes, I have taken the sleeper in the past.
It leaves London Paddington at 23:45, but there is a lounge you can use if you arrive earlier ("access to the GWR First Class lounge at Paddington from 21:00").
I don't think there are connecting doors between the cabins. With two adjacent cabins you still have to go into the corridor to get from one cabin to another.

For more info, including photos and a video, see the "man in seat 61"'s page on the Cornish Sleeper: https://www.seat61.com/Cornwall-sleeper.htm

CORRECTION I lied, according to the man in seat 61 there are connecting doors (memory failure!):

Inter-connecting doors between sleeper compartments...
There is an inter-connecting door between each pair of adjacent sleeper compartments, normally kept locked shut. You can book two adjacent 2-berth compartments with an inter-connecting door between them to make a 4-berth suite, or you can book two adjacent single-berth compartments with an inter-connecting door to make a suite with two lower berths (but 3-berth suites aren't possible because of the way the compartments are paired). You can work out which berth numbers have the connecting door like this: Berths 1 & 2 have a connecting door with berths 3 & 4. Berths 5 & 6 have a connecting door with berths 7 & 8. Berths 9 & 10 have a door with berths 11 & 12. And so on, up to berths 21 & 22 having an inter-connecting door with berths 23 & 24. Travel tip: When asking for two compartments with an inter-connecting door, ask which berth numbers you've been allocated and make sure they are indeed two communicating compartments before hanging up the phone, as telesales staff don't always get it right. However, on board staff are excellent, and can usually sort out any problem.

Thanks to those that replied for your insights

training? that's what athletes do before an event!

The obvious questions which follows yours are how would you get to Penzance to start with? And why would you?

There may be pirates there.

Sam, there are: http://www.cornish-pirates.com/