Trains and buses.

no train or bus strikes have been announced yet for September

There is no direct train from LHR to Bath. But there is a direct bus via National Express.

What Frank said.
My husband and I have have taken the bus/coach from London Heathrow bus/coach stations to Bath many times and have always been happy.
The seats on the buses/coaches are comfy--more comfortable than seats on planes--and there is free WiFi onboard.

Big pluses: You can see more from the bus than from the train. You sit up high and are not down in a cut like sometimes on a train.

Generally speaking, the buses are much cheaper (fare bought on the day of travel) than train fare unless the train fare is bought online far in advance.

Thank you Nigel, Frank II, and Rebecca for the information. I think I will take the bus based on Rebecca's tip. Last time I took the train. Now that I know how to get there, time to find a place to stay in Bath. I will be solo.

Should I buy a National Express bus ticket on day of travel or should I buy in advance online? If I buy online, is an electronic ticket sent?

It would be much easier to go into Windsor and stay, it’s a 15 minute taxi ride. Why travel another two hours to Bath after traveling all night., it’s crazy.

"Should I buy a National Express bus ticket on day of travel or should I buy in advance online?"

They are not expensive, I'd buy on the day of travel unless you look at the National Express site and see a huge difference in fares for tomorrow and fares for a month away. I haven't bought one since I changed over to mostly digital so I don't know about an eticket.

OP posted this in August with travel in September. Liz, I hope you had a wonderful time!

Robin Z, I can't speak for Liz, but we don't like unpacking and repacking. I'd rather get to the hotel in Bath and collapse, knowing I'm at my destination, than deal with an interim hotel for a single night. We'll get some sleep on the bus.

Pam, thanks for the pricing info.

Regardless of when you go, or where you go, if there's a strike you're at their mercy. Out of your control, which is why you have a plan B and plan C.

Thank you all for the advice. Good idea to have plans B and C.

Pollyannpax,

Yes you get an e ticket from National Express, the driver just scans the QR code on the ticket. You can print it off if you like or just show it on your device. The vast majority of pax now just show it on their device.
In case something happens with my device I always make a note of the ticket number, as with that information the driver can always find the ticket on his machine if he needs to.

If you buy on the day then prices are about double what you would pay in advance, and on train strike days they about double again, as there is a captive market. You are also unlikely to get a walk up fare if it's a train strike day as they will be running to capacity. Train strikes are announced at least two weeks in advance. The coaches start from London so any spare capacity they had on strike days will have been filled at London.

It's a difficult choice if you are connecting out of a flight which may have it's own problems, but on balance it's worth booking in advance.

phred, thanks. This will be our first time using mass transit; I never considered strikes. How common are they? Are rail and coach the same union; do the employees of them both walk out in coordinated strikes, or do they usually strike separately? What the best approach to plan for strikes?

Thanks for any guidance.

What the best approach to plan for strikes?

By not fretting about it. Unions have to give a fortnight’s notice in any case. And strikes may be settled by the time you get here.

Keep an eye on UK news is all you can do.

National Express Coaches as a company don't strike.
National Express own very few coaches. Almost all services are franchised out to other smaller coach companies, but all in the same livery.
Generally those employees are not unionised.
City bus and London bus services are unionised. So there is a wave of strikes currently on various London routes and there have been strikes at various local bus companies round the country.
But the long distance coach services have not been affected and it is hard to see how they ever could be.
It's the trains which you need to worry about.
When the trains do announce a strike book coach tickets quickly as fares rise exponentially on strike days and they sell out.
Coaches run direct from LHR to Bath broadly every 2 hours with a mid morning gap.

Thanks isn31c, that's what I was looking for. My plan A is to buy the National Express coach ticket in advice with the Change & Go option for 5 GBP. I like the thought of a direct trip to Bath from Heathrow, then taking a cab to my B&B. The RS tour starts the next day so I'll have time to recover from jet lag.

isn31c, I'll echo those thanks. I'd already planned to book the coach to Bath with the 'Change and Go' option anyway. Right now we don't plan on using any of the local bus systems, and we have nothing locked in that we couldn't drop if the trains are indeed not running.