I'd imagine that BTC asics would be your best bet. Hoover up the ones off ebay, cos nobody who's paying for power can run them in the UK anymore. Or order new from Sh**main.
The new algo asics are in high demand and subject to forks and all sorts of malarkey, making them higher risk. A barnload of S9s will gradually turn a profit for very little outlay, and need little maintenance vs gpus.
i was thinking along the same lines as you as in buying Asic's that are unprofitable in most western country's rather than risking with brand new ones to start but either way i will be needing dozens of them. perhaps a better question is what is your asic and how much is it making per day before electricity and what is it mining at least that way its tried and tested
As someone already pointed to, whattomine will answer that, obviously those figures will gradually decrease. Fact is though, there are plenty of BM machines in the UK that are being used as doorstops, so hunting those will serve you well. Maintenance is the big question, but at least s9s are relatively easy to pull apart and post back to China. Keep it cheap and start small, see how you find it.