If I was to fly into Heathrow, is there a direct train from there to Bristol? And if so, which one and about how long is it?
Heathrow is an airport.
You’ll need to take the Elizabeth Line ( London Underground ) to Paddington Train Station and take a Great Western train to Bristol.
bus/coach from Heathrow to Reading, GWR train from Reading.
There are two main stations in Bristol, Bristol Temple Meads and Bristol Parkway. Know which you need and make sure your train goes there.
There are frequent National Express coaches to and from Heathrow, and that is the way we usually go.
You may also find it worth looking at Megabus. The train involves making connections and may take longer and cost more.
You can go all the way from Heathrow to Bristol by train but if you take the Heathrow Express into Paddington, it will cost you a lot more. Go to https://v3.trainsplit.com and put in for your journey from Heathrow to Bristol (Temple Meads is the city centre station whilst Parkway is to the north of the city). Choose ‘Advance’ and then Avoid London.
It will now give you a route that takes the short hop to Hayes & Harlington where you change trains for a stopper going a few miles west to Reading where you catch an express to Bristol. Note that with an Advance fare, you need to be on a specific train when on the express. Note that the fare is cheaper if advance booking rather than on the day. Also check out return fares v buying one way tickets. (You might be better off buying an anytime return between Reading & Bristol if not knowing when you will arrive & planning to return or go to London later. The short hops between Reading & Airport could be paid separately).
PS. The trains that call at Bristol Parkway are usually going to Cardiff/ Swansea.
Make life easy for yourself.....take the bus to Reading then switch to the train to Bristol.
No backtracking, no multiple changes.
Hayes and Harlington, West Drayton and Slough are served by public bus from heathrow.
Use contactless bank card to take any train to Reading
Board the train to Bristol.
You should find a few Hitachi train (the rolling stock serving Bristol) at Slough
If you take the Railair coach to Reading book it separately and not as part of your rail fare.
There is a direct coach to Bristol from Heathrow though every hour from T5 (ten past) and T2,3 (half past) through the day.