All with profits funds 'add' any bonuses upon maturity, transfer, death....
Not an attempt to encourage you to transfer, simply how the figures are expressed. The annual reversionary bonus is included in the fund value, terminal bonus varies from year to year so can only be stated when you ask for figures.
You need to check the current policy details, what bonuses have been paid (lots have cut these drastically), are there guaranteed annuity rates (current rates are approx 5%, some policies have contractual rates in double figures. The longer there is until retirement the longer you have to reap the rewards of lower fees, possibly better performance.
Longer term you might be better of transferring to a SIPP, but just check you're not giving up a good thing.