Depends which model you want. The Mk1 is great, the Mk2 is harder to find. Mine is a 2000 Black Aristo V300 Mk2 on a W reg so cannot be imported until 2010
Try to find one with low mileage good condition and all the MOT's a service history is good. GET A HPi report!! To save money, get one already in the country
Autotrader is best, avoid Ebay due to most of the cars are naff and have bad history. Ask on the Aristo forum too Clubaristo.net. I'm a VIP member there. Best place to find out which model you want.