SW England home base for visiting cathedrals

Bristol would work pretty well, I think.

I second the motion for Bristol. Another vote is for Reading. Close to London but cheaper and has excellent rail and bus connections. Last October I used it as a base to do day trips to Winchester, Oxford, and Salisbury. I stayed in an Ibis that was two blocks from the train station. Very convenient.

The problem with staying in a small town like Marlborough or Hungerford is that they aren’t really well connected. Generally public transport will predominantly be designed to take you to the nearest big city where people go for work or hospital appointments. It will require a number of connections and a lot of travelling time to get to places further afield.

If you stay in a city like Bristol you can get to all the places you’ve mentioned using 1 train or bus with no changes.

Either Bristol or Reading would work but the former is quite a lot more interesting to the visitor itself and has its own medieval cathedral as well.

Bristol is a lovely city and it has one of my favourite cathedrals. The cloister and chapter house are still very well intact. Gloucester is another one you ought to see if you can. They've got a Whispering Gallery which goes along the side of the cathedral behind the great window, and a cloister where Harry Potter was filmed. Also unique wire hanger arches and interior buttresses which add to the eclectic nature of the cathedral. Gloucester is reachable for a day trip from Bristol.
Not to mention that if you do want to see Glastonbury Abbey you will need to go by bus. I don't know the exact way to get there from Bristol, but I know from Bath it's the 173 which also goes to Wells after Glastonbury. You can reach Bath easily by train from Bristol.

Winchester and Salisbury are amazing. Glastonbury was OK, not as amazing as I expected. The cathedral at Wells was interesting.

There a bus from Bristol to Glastonbury, the 375 or 376. Both make a huge number of stops en route so be prepared to settle in for a tedious ride but it does get there eventually.

Bristol is also home to St Mary Redcliffe church which visitors can easily mistake for the cathedral as it’s very large and very old. Elizabeth the first was a fan.

St Mary Redcliffe also has a most impressive ring of 12 bells, the tenor at 50 Hundredweight in B. Most of the bells are from John Taylor in Loughborough - who make the sweetest bells - cast in 1903, but there are two significantly older ones, the number 10 from 1763 and number 11 even older, from 1622. The ringers have won many a ringing competition.

I see Gloucester mentioned but I am surprised that neither Worcester (easy by train, riverside, exquisite, very historic, another magnificent ring of bells) nor Hereford (easy by train, Chained Library, Mappa Mundi!!!) were mentioned.

If they fit, they are both special, and for me really worth a visit.

Reading had a lot more biscuits than Bristol

Yes Nigel! Can't believe I didn't include those in the first response. I second the recommendation for Hereford and Worcester.

St Mary Redcliffe also has a most impressive ring of 12 bells,

Oh Nigel, you just brought back one of my favorite memories of my tour of southern England. We stayed in Bristol one night right by St Mary Redcliffe (a wonderful church by the way) and I'm not sure what the occasion was but that evening the bells started ringing and my roommate and I, who had a room facing the church, thought "oh, isn't that nice?" Those bells rang on for 15 minutes straight and my head was ringing by the time they were done.

I'd definitely stay in Bristol for visiting those cathedras and other historic buildings. If you do stay in Bristol do visit St Mary Redcliff.

Another suggestion is Bath and you could see Bath Abbey of course. We have traveled by train from Bath to Salisbury, and to Wells and Glastonbury by bus, and found the countryside from the bus to be beautiful. From Bath it is 15 min to Bristol to see churches there.
We will be taking the train from Bath to Winchester tomorrow.
We love walking the canal in Bath and going up to the Bath Skyline. Beautiful!