I’m thinking of buying a new unicycle after my trainer uni but i don’t know where to buy or what to buy 
www.unicycle.uk.com should sort you out, there really isn’t anything else UK-based as far as I know. Municycle.com (from Germany) ship to the UK also so might be worth a look if you can’t see anything you want on the first site.
Definately Unicycle.Uk.Com is your best bet.
If your unsure of what you want, give them a call and they will help get the best unicycle to suit you.
Joe,