installing timber (jeld wen) window frame

[dan1]

Hello! I'm planning to remove perished UPVC window replace it with a timber one. What should I stick in the gap between new frame + wall? Some kind of expanding filler? Do I then have to put a sealant/filler down the outside to ensure weatherproof? Any advice + recommendations re brands would be much appreciated (I'm aware of need to comply with building regs + poss get planning approval)
Thanks
Dan

[stoneyboy]

dan1,
Pin the window in place with 2 screws per side - use packing pieces.
If the gap is more than 5mm fill it with foam and then use frame sealant.
end

[dan1]

Thanks for that Stoneyboy.