There are a few areas of disabled parking spaces at Bristol Temple Meads railway station. Some are in the short-stay area at the front of the station, and there are some in the long-stay parking area. Parking is free for people with blue badges as long as you park in the designated spaces
I realised how much I appreciate the long-stay ones when I returned to my car yesterday. The bays are in a covered area of the car park so the car was wonderfully cool. That part of the car park is on a level with the ticket office, departure boards and main entrance to the platforms. You have to use the subway and lifts to get to most of the platforms. The disabled spot furthest from the automatic doors into the station proper is about 20 meters, and the ticket to the first platform is only a few more meters away from there. Wheelchair users should find navigating the station relatively easy - the staff are very friendly too. I don't use a chair so it's a 'person with a stick's view of the station.
It's in a busy area of Bristol and you have to negotiate traffic and pedestrians to get to the long-stay parking. There are lots of 'rubble' type car parks we know and love in Bristol where they've knocked buildings down, levelled the ground and opened them as Car Parks. Those Car Parks are gradually being build properly.
If you want to park in Bristol to visit the city centre the railway station is not very useful for people with mobility problems as it's a mile or so away from the centre. But there are always taxis at the station.