its not a bad price at all mate, new (secondhand) engines usually go for around the £600 mark. plus turbo plus fitting.
sounds like a good enough deal to me.
make sure your exhasut gets a good and proper clean out mate as all or most of the oil that blew through the engine will be lying in the exhaust system.
also make sure your intercooler is well cleaned out too as there could well be oil in it too.