Get the Nokia Thetford freepost service centre address off the website, send it back and they'll re flash it/repair it or whatever and return it in a week or so. Keep your battery, Micro SD and back cover though.
You can track the entire progress on the website too.
When I sent back my E61 (covered in dents on the magnesium case) after a failed update they flashed all my data onto a brand new handset and sent it back pronto. Very good service.
I imagine with an E71 they'll be uber quick and just bash you out a new handset with latest firmware, it'll probably come back minus any Network branding on the handset too which make resale values better too.
If you have the chance to do a backup via the data cable give it go, this may work even if the handset doesn't boot properly.
Also I believe under European law a 24 month warranty applies to pretty much all handsets if used for their stated purpose.