CyBoxter - as per Radium King: there are 2 excellent engine suppliers in the UK,
Autofarm (
www.autofarm.co.uk) and Hartech (
www.hartech.org.uk).
Both have an enviable reputation, as does Flat 6 (site sponsor) in the US. They can supply fully overhauled engines with warranty & I would strongly recommend you contact all 3 of them to see what they can offer before you decide to run the gauntlet with an unknown second hand engine - you live a long way from the supplier and need confidence in the product before handing over your money....