My husband and I will be traveling in October by train from Bath on a Wednesday to leave from Heathrow the next morning. Is there a hotel near the train station that would then get us to the Delta terminal (4 I think)? Or will we just have to get a cab from one end or the other?
Consider staying in the Yotel right in Heathrow Terminal 4. See RS "England" guidebook and yotel.com. We stayed there once before a morning flight from LHR Terminal 4 and were very pleased.
You didn't mention how early your flight is. The train from Bath comes into Paddington. If your flight departs at 8:30 am or later, you could choose a hotel in the Paddington area and either take the Heathrow Express in the morning (the first departure is shortly after 5am). I stayed at the Hotel Indigo Paddington last year and was very happy with it, but I used points; I'm not sure that I'd pay rack rate for this hotel. There are many others hotels in the Paddington area. If your flight is extremely early in the morning, then staying by Heathrow would be a good choice. Personally, unless I have a very early morning flight, I prefer to stay in London. It gives me an opportunity to enjoy an evening in London (dinner, theatre, etc.).
I stayed in August at the Ibis and took the free bus to the central bus station, then the free train to T 4. Including the walk from the Ibis to the bus stop (Harlington Corner), it was about 25 minutes.
Have you considered a bus? National Express runs a coach every two hours from Bath to Heathrow with fares beginning at around 34 pounds if you buy them early enough. http://coach.nationalexpress.com/times-and-fares.aspx?searchId=b3081722-4843-4206-bec8-e89a01f191e4
We decided to stay in Windsor and tour the castle in the afternoon before leaving in the morning. It looks like the bus to Windsor takes hours and hours. Bus to Heathrow then bus to Windsor?
Train to Paddington to Windsor? There has to be an easier way!
Bath to Windsor is around 1 hour 50 minutes by rail. Change at Reading and Slough.