Sorry Whickerman, this is the part of the insurance industry I work in - fraud. We were considering offering cover in the Republic, but we've managed to persuade the company otherwise - it's too big a risk. Whilst most of the major insurers operate there, it does not necessarily reflect the findings of surveys that I have seen in regards to fraudulent activity - a prime example being a case of one man allegedly paralysed in an accident. The investigator was convinced he was faking it, it went to court, and he got a multi-million payout. The investigator still wasn't happy, and continued to follow him in his spare time. Months after the payout, he boarded a flight to Lourdes - he entered the water, and miraculously could walk again. The courts upheld the payout on the basis that he ''wouldn't have lied about this being a devout catholic'' (I am catholic myself). They still have a photo of him on a dartboard in the insurance office.
Fraud in mainland UK is bad enough (I think we need to withdraw all cover in West MIdlands, Luton, and East London personally), but it is simply less prevalent here, and easier to prove.
Channel Islands - pass, no idea.