It all works out. There's nothing else to pay (including ferrying if the maintenance is being carried out away from home base, which any of us do) as everything other than the replacement engine comes out of the fund (as you say, about £80ph). This also includes a float for unforeseen expenses, and there are a few.
Out of interest, not sure how other groups do it but the £150 per hour is airborne time (it's recorded on the meter as time exceeding 55kts) as opposed to block time. It makes sure no-one is in too much of a hurry to get airborne and takes the time to warm up the engine properly - which saves a few bob in itself.
Also, most aeros sorties are around 40 minutes block which equates to about 25 minutes airborne and hence about £62. If you look at it that way, a block hour (typically 45 mins airborne, which is long enough in one go for me) works out at £112. Compare that to your flying club Warrior.
Works well for all of us and Ed certainly doesn't have is hand in the till, although he may need to get a job soon.....
