Insulate an Already Converted Attic?

Hi,

Im in a 1970s semi-d, previous owners pumped the walls with the little grey beads and I am mostly happy with the heat retention however my bedroom in the attic with an en-suite and an office up there is absolutely freezing in Winter, like literally the same temp as outside.

There is rockwool under the floorboards up there but not much else as far as I can see, access to the rafters is through 2 small doors under the eaves either side of the bedroom, typical attic storage access (will add pics tomorrow).

Just wondering what my options are here? Im not going to rip the whole thing out but is there any company that will go in under the eves and install foamboard or blow a load of foam in there or something like that? Would there be a grant for this?