For sale on ebay is a Kris Holm Trials / Street Unicycle: http://www.ebay.co.uk/itm/170701900103?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1586.l2649#ht_500wt_1325
Follow the link for it’s specs and for pictures.
It’s been well used but it’s still in good condition. Everything is tight and strong and runs smoothly.
It’s local pickup only but if you like you can arrange for a courier to ship it anywhere in the UK or in the world (not sure how much this would cost you).
The start price is 99p so you could grab yourself a top unicycle at a very low price!