You can get policies where you set the growth rate, or some will link to RPI.
Many will give you the option of 'taking or leaving' the increase offered, although most will say that if you decline the increase two years on the trot they will cease offering them
There is a serious 'see an IFA' point to worry about though.
Many policies that will link the cover to RPI will have the premium increase by more than the cover increases.
For instance, one I looked at recently had the cover increasing by RPI but the premium increasing by RPI + 2.5%
You may need to ask your IFA to check this, is obscure enough to be overlooked, and while this year or next it will make little difference, in 15 or 20 years time it will make a fair difference. As this forum proves, there is never going to be a time of life when money doesn't matter (unless you are very lucky).
Hope that helps
Adrian