It's possible that the timing chain might have stretched or jumped a couple of links (maybe three) as on the Z22YH the exhaust sprocket has a sensor for the cam timing which would cause the engine not to fire, or the valves are not closing completely causing no compression (and possibly valve damage).
Did the AA do the compression tests ? Do you have the results ?
Not much of a mate if he wants £300 just to look at it ! :eek:
A good starting point would be to remove the camshaft cover and check the timing chain is still intact and that the front guide hasn't broken. 🙂