you can apply for ILR (thats if they dont change immigration laws which effect this in july 2011) upto 28 days before you've been in the UK 2yrs !!
you can go back to the phils anytime you want, but try not to spend more than 90 days out of the uk each yr. thou you could spend longer, but the longer your out the chances of refusal increase, as the UK is suppose to be your home
you have to apply for ILR or FLR before your current visa expires..