LHR to Bath

There's an express bus. We were going to take it on our trip to May but now our AA flight is arriving later in the day so now I think we will spend the first night in London and go to Bath the next day. https://www.nationalexpress.com/en/destinations/bath/heathrow-to-bath

There is also a train every 30 minutes- a through fare booked in advance is around £35.
Take the Elizabeth Line 1 stop to Hayes and Harlington, change to the opposite platform for Elizabeth Line to Reading, change there for a train to Bath. Overall journey time around 2 hours.
It is much easier than it sounds.

Clearly the coach is easier and cheaper, as it is no change, as long as you are willing to wait- as they are every 2 or 3 hours.

We're planning on taking the coach each way in May. When you buy the ticket, there's an inexpensive option for flex scheduling. As I understand it, it allows you to get on either earlier or later than your reserved time. So if the plane is late or you get hung up in Customs, you can get on the next bus.

We are also planning to take the coach. We arrive on a Tuesday at 9:15. The next national express bus is at 10:30?
Do we have enough time if we don’t have checked luggage?
Should we wait and not buy tickets, and if we miss the 10:30 take the train instead?

I think that is very tight, especially if you are landing at Terminals 4 and 5, meaning you have to transfer to T2/3 for Central Bus Station for the coach.
Personally I would have a rule of thumb of 2 hours. Your luggage isn't the problem, as much as crossing the border.

If I were you I would book the coach ticket with the flexible option- costs a few pounds more. Then if you know at your home airport that the flight is late, change the coach before boarding the plane (to the 1425 or 1635 if very very late).
Actually the 1030 coach is a change at Bristol onto the X39 back east to Bath. I would book the 1225 direct bus which arrives only 30 minutes later than the 1030. That gives you a decent buffer.

The benefit of the train is that it calls at all terminals.

It is rather untried if the coach ticket can be changed after it has departed.

Wonderful info. Thank You!!

Thank you very much isn31c.

What if we tried for the 10:30, since we arrive at terminal 3, then if we don’t get there in time, take the train?
What is the best train route? I have read here about going to Paddington on the Piccadilly line, but also about going to Redding.

The Piccadilly line doesn't go to Paddington. It's the Elizabeth line you want, or the Heathrow Express, which is a few minutes quicker by double the price unless you can get an early discounted ticket.
But the best way by train is now to take the Elizabeth line one stop to Hayes & Harlington and change for another train on the line to Reading. From here you can pick up a direct train to Bath. It is also possible to take a coach to Reading station from Heathrow but I think the connection via Hayes & Harlington is preferable.

You can book the 1030 coach if you wish.

If you buy a through train ticket at Heathrow to Bath the route outlined by John is the one you have to take, you aren't allowed to travel via Paddington.
Make sure you go to the Elizabeth Line/HEX platforms, not the tube platforms.

I'm also looking to go from LHR T5 to Bath but am trying to find a car service that will take us to Stonehenge on the way. Any suggestions/recommendations? I've tried Celtic Horizons (recommended in Rick's books) but they are booked for the day that we arrive... Thanks in Advance!

A lot of people on here recommend Blackberry Cars- https://www.blackberrycars.com/

Their fixed rate to Bath direct is between £175 and £240, would obviously be more to add in Stonehenge.

If it was a direct run you could book it on line.

That may or may not be the best day to visit Stonehenge, when you are likely to be jet lagged, so less able to take in fully the whole experience.

Here is a quote from the National Express Website about the "Change and Go" feature.
"Change & Go allows you to have complete flexibility and offers you peace of mind if you have missed your departure. You can switch to another service within the 24 hour flexibility period (12 hours pre-departure or 12 hours post-departure), note this is subject to availability. Customers are able to make one free amendment to both the outbound and inbound journey, only the time/date can be amended where no fees or excess fares apply."

The cost for this service is 5 pounds extra when you book. You could book a National Express bus in advance and know that if you missed it due to a late flight, you can simply get another one within 12 hours.

Carol's quote is intriguing me. Because it also says that to do the change you either have to call NatEx or go into a Coach Station.

Whereas I always book a flexible fare, which I can change on line myself, in my account if I pay £5 at the time of change, but not otherwise. I used to book advance fixed fares but on a Senior Coachcard flexible fares are usually cheaper now.

So it sounds like there are two different systems. I have 2 forthcoming NatEx trips, but daren't experiment on those as I'll probably inadvertently muck those bookings up completely