Thanks ideally 10 minutes away as I will need to jump on a Train to get back,from memory the walk into central Bristol seemed longer than 20 mins
But equally if the Girl is worth it I can always take a Cab
You're going to be challenged! Within a ten minute walk of Temple Meads, there's only a few new flats in the area behind the casino, and in the residential area near St. Phillip's church. I believe there's a few SPs that might work from that latter area from knowledge going back several years, but it's mostly either a) offices or b) under re-development around Temple Meads.
Bath Road parlour's a short journey along....Bath Road (!), which is less than a 10 minute taxi journey in good traffic. You could ask the driver to take you to the ITV Studios or Sainsburys on Bath Road if you want to be discreet.
Other than that, you'd be better off finding an SP working out of either Cabot Circus or a Harbourside apartment both of which are a ten minute taxi journey outside of rush hour (is that still a thing?), or a 20 minute walk as houseboot said, maybe 25 if you take it easy.
With regards to central Bristol, you can reach the Castle side of the centre in 20 minutes walking from Temple Meads, if you go out of the side route AND get your skates on. But central Bristol's a large area, so you could easily add another 10-15 minutes to that if you're heading for the hospital or Park Street area, and that side's uphill too. Steep uphill.
