Hi, I'm in the UK too. The Juwel Trigon 190 is roughly 40g so not big enough for some species, some may fit though. I think your first problem is that it is really hard to get any certain species in this country, nobody can identify anything but mimics and blue ring, so anything else is sold as just plain 'octopus'.
Have a ring round and see what you can get hold of first, then it's easier for people to recommend.
Whereabouts are you btw? I'm in Birmingham so if you're midlands based I can give you a basic idea of what we can get around here.