Big fan of the military and industrial heritage stuff myself. The UK just has so much obsolete military stuff its hard to avoid, plus its a good starting point for underground. Grown quite fond of new developments and infrastructure too - sometimes it's nice to do a 'clean' explore. Not really a fan of proper shitehole derps, the collapsing houses or smashed up stuff unless it has a particularly good history. As for rooftopping I've done a bit but always found it to be quite a difficult and different genre to try and penetrate.
Something else of note, I've always actively preferred stuff nestled amongst the outdoors as opposed to big interiors (as cool as they are sometimes). I get a lot out of seeing these things ruined amongst the landscape and generally prefer those kinds of shots and the way they relate to their surroundings.