http://scoobyclinic.com/performancetuning.htm
'The process starts starts with the engine out, strip down, asses and report, if 400 BHP is the figure we are after it is a lot cheaper than 450 BHP as we don’t have to strip the bottom end, just heads off, new forged drop in pistons and back together using ARP head studs, and all new gaskets. Cost wise approx £2K + vat to do this.
If 450 BHP is the ask then we have to go further and strip the whole engine adding con rods and new bearings at the same time, add £1500.00 + vat to the £2K.'
It approx figures but costs escalate when there is damage, do it before and its no where near as costly.
As far as costs you do realise i have only just had mine rebuilt so well aware of what they are?