It was about £6k for an IO-540 a few years ago. And that was done by a well known cowboy (since gone bust) in the UK. It's really hard to find a reputable engine shop in the UK; I would send the engine to a specialist in the USA.
Plus the cost of the prop. Often, the hub had to be replaced and then a whole new prop probably doesn't cost any more. Mine cost £12k or so (with a JAR-145 form of course
).
That's why one needs to be a bit paranoid about driving on grass, and especially grass/hard transitions. The renters queued up behind (paying brakes off to brakes on) may not be happy about you getting out and checking the ground for potholes but that's what you have to do. The airfield which owned the pothole can probably be sued but in practice will do absolutely everything possible to wash its hands of any liability. The insurance pays out but it knocks your premiums for years. Been there, done that
