Personally I used to have a policy through Traffords, (Global) but have now moved to BALPA's policy for a few reasons.
My company has instigated "self-insured" coverage for both loss of licence and PHI. i.e any claim will be paid from the pocket of my employer, so I will be on my own trying to fight my employer to get a payout. Also, they have introduced various exclusions, which are quite ambiguous, and legal advice has suggested that unless you were sitting at home quietly (which I don't do very often) and something fell on you, any accident or injury could be argued against.
The other reasons though were that BALPA's policy offers the chance of upping your premium very slightly and getting temporary benefits after only a 3 month waiting period. If the temporary benefit is paid, it does not have to be repaid if you get your licence back before the 2 years is up.
Also, it has no exclusions as far as activities go so you can go skiing, sailing, quad biking to your heart's content and not worry.
Finally, you can pay monthly and I don't think it cost any more than paying a lump sum, or if it was, it wasn't very much.