these days people are so obsessed with doing everything online, but some things in life still need to happen in the real world. finding an engine is one of those things, especially if you want it quick, cheap and local.
first go on yell.com and get the number for every breaker and dismantler within X miles of your postcode (increase X if your first attempt doesn't succeed). next ring every last one of them, it will take an hour or so, but its much beter than driving to all of them. job done you know who has what you need, next you go visit every place that has the engine you need so that you can get the best one, and then negotiate the best price.