Welcome to AD, Wolf.
I'm surprised no one has commented on this yet.
I think this is a good domain personally on a good TLD extension and could easily fetch from £XXX
bare min. (re-seller) - £XXXX+ to the right end buyer.
I'm not entirely sure about the tourist trade to Belfast etc or as a holiday destination but I'm guessing it's going to be reasonable at least (e.g. Travel Agents or even Airlines, etc), but I would imagine a local company or similar would hopefully be interested in this or even the local authority (council), etc. There are almost 28 Mill results in Google for 'Belfast' at the time of this post, making this a generic and potentially very in demand DN (all other main ext. are also gone).
I think this is the kind of name that you need to fire off a couple of hundred e-mails (minimum!) about, directly and see if you get any response. I see you've had previous offers via SEDO and I assume they were not offers high enough for what you wanted (out of interest, what were these if you don't me asking that is?!

).
Personally I'd take it off SEDO first, develop it, then go for the kill directly.
Good luck.
