In regard to the two old hotels near Temple Meads, I climbed onto the roof of this one (51.449361, -2.585380) a few years ago and the midday view was gorgeous. I was alone so didn't go in but access did look easy. The scaffolding has since been alarmed but that needn't stop you. It is called the Grosvenor Hotel, was apparently built in 1875 and became derelict in 1993.
This bloke in Flickr seems to know some of its history.
The derelict building next to it was called The George Railway Hotel and is Grade II listed. I've never been in there as it looks like they've done a good job sealing the place up but one day I'll give it a go. Apparently, it is "One of only a few large, decorative late Victorian public houses in the city." Read more
here
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