Not you going wrong, O2 have withdrawn the 1.11.170 ROM because of the connection and stability issues mentioned elsewhere on this site.
If you want stability and don't use Blackberry, use the ROM I made that can be found on this site. Have a look in the few recent threads here and you will find them.
Sorry to hear about your problems, hope they're sorted soon for the better.
Take care of yourself,
XDA IIS - Custom ROM - Gone
XDA IIi - Custom ROM - Gone
XDA Exec - Custom ROM - Gone
XDA Orbit - Custom ROM - Gone
XDA Orbit 2 - Custom ROM - Gone
XDA Ignito - Custom ROM
XDA Guide - Custom ROM - Gone