well depends what you mean by exotic? I always thought that meant non-native wildlife

well here is a site where people have mailed in to give a list of organisms

http://www.bbc.co.uk/blogs/natureuk/2010/06/have-you-seen-exotic-species-i.shtml

and here is a website that details lots of them plants included
https://secure.fera.defra.gov.uk/nonnativespecies/factsheet/index.cfm

so lots is the short answer and these sites give much fuller lists that I could

really good question though..enjoyed looking it up

see now i am thinking whther bacteria could be considered native/non-native

although its been found for a while that we all have our own natiuve bacteria the microbiome as its called..that may be used one day to track criminals
http://www.dailymail.co.uk/sciencetech/article-1258253/Experts-track-criminals–tell-tale-trail-germs.html

bit off topic but cool i think

Ooo! That’s a good one, I’ll think of the ones I know, but reckon there could well be more information on the web. By exotic do you mean foreign or just plain unusual? I’ll try and give a flavour of both.
I know there are wild wallabies hopping around somewhere, ringnecked parakeets flapping about, I’ve heard there are raccoons, snapping turtles and, rather worryingly, some sort of scorpion. More mundane species include the American Crayfish that is out-competing our native species and the classic ‘invader’ has to be the Grey squirrel. Even the humble rabbit was introduced by the Romans, so does that count as exotic?? In addition there are Mink, released from fur farms, they are now quite well established in Staffordshire; they’re rather vicious. My Mother-in-Law lives in Staffordshire and one of her cats had an hour long fight with a Mink a couple of years ago, quite a battle.
I haven’t even mentioned plants, insects and birds, that list is huge and growing due to climate change. See what you can find out, I’d be very interested if you could find a definitive number.

I am not sure what types of exotic wildlife there is in Britain. I guess there will be a lot of migratory birds that come here during the summer and leave us in the winter for hotter places like Africa. There may even be some birds that leave us in the summer to go north in search of colder conditions.

Aparently there are panthers/pumas (or just wild cats) in Scotland. Also in the northern Scottish seas there has been Orca (killer whales) and sharks found!

In the rest of the UK there are some non-native animals including raccoon dogs from East Asia, yellow-tailed scorpions from Italy, ringnecked parakeets from India and Australian red-necked wallabies but I can’t say I have seen any of these.