How much is "reasonable" for various charges?

Tenancy Deposits

Can anyone say what level of standard charges is "reasonable" to put into tenancy agreements for things such as:

1. tenants lose individual keys (it costs more to organise it all than just the £3 at the key cutters)
2. tenants lose bunch of keys - so we might have to change the actual locks
3. tenants lock themselves out - usually at 9pm on a Friday night - and expect instant response to let them in
4. exceptional amounts of cleaning after check-out

Should it be calculated using hourly rates? What about mileage?

If we cannot easily charge for our own time, can we use a flat-rate fee structure?