Get in touch with the major providers NOW and ask for details. You can find information in the RHQ and finance threads.
What you need to buy will be dependant on your personal circumstances, so it is not possible to give specific advice over the internet. Make sure you speak to one (or several) of their advisors and seek guidance.
Do it now, because some of them have a moratorium (ie you cannot receive full benefits until you have had the policy for 6 months), so if you only buy it on the day you deploy, you will not have full coverage throughout your tour.
Both PAX and Service Life Insurance can be arranged at Chilwell and there is no delay over coverage, however the rates vary between the two on the life aspect and will depend on the amount of coverage required and your circumstances. Cannot stress highly enough need to have soem persoanl injury insurance no just during teh tour but we had a few people injured during the PDT and will have issues for a very long time - 1) the Army will simply not pay out enough if you are injured 2) I had some kit knicked when I was in Musa Quala this year and PAX have paid up already ie 3 weeks from claim (but they are replacing everything not a cash payout).