Boo was bang on the money about the Excavator. It's a 700+ set, with (not pneumatics but driven movements), scope to motorise it later, an alternative build, and overall a damn nice model!|
Plus you can get it with a decent discount from John Lewis, or Amazon if you're feeling lazy but patient.
IF I hadn't had 42006 on the go, I would have jumped on the Crawler (9398) for £100 (1,300+ pieces, motors come in the box, and it's got a very good alt build).
I do love that Crawler though!
PSN ID: Djini
Nintendo ID: 3454-3147-0073