Well, I finally got my M8 back from Regenersis HTC repair centre and I'm very surprised.
The total cost of repair was £103.31. I was expecting at least twice that amount as the phone is good as new especially considering the difficulty of the repair.
They have replaced the LCD, the bottom speaker panel, the middle assembly and the back cover. I'm quite impressed really as HTC were quite helpful whenever I contacted them and the whole thing has been pretty painless. It took less than 3 weeks from sending to receiving. Thumbs up for HTC
The breakdown of parts:
LCD & touch- £43.06
Bezel pre assy - £5.58
deco plate upper assy - £1.17
Deco plate bottom assy - £0.89
Labour - £22
Shipping - £11.29
Not sure which one of those is the back cover, but it's been replaced!
That means that HTC charged about £50 +VAT for the actual repair. The parts themselves cost double that. No point in buying insurance at that cost.