Bugaboo Bee: Do I need the seat liner AND the footmuff?

[SoLongAsItsHealthy]

I have been using the cocoon since DS was born but now, at 6 months, we need to move onto something roomier. I want to get the footmuff for winter but am wondering if I need the seat liner until it gets cold enough for the muff. Is the seat liner any good?

I got a John Lewis footmuff for about a quarter of the price of the bugaboo ones in a lovely stripy pattern and it worked brilliantly, plus it unzipped so you could leave the bottom half in place if the whole footmuff experience wasn't needed or zip the top back on if it was cold.