I have some nice Sram 11 speed stuff gathering dust, namely an xx1 cassette and a force rear derailleur, is it possible to use a flat bar trigger shifter with the force mech? I’m looking to upgrade my lads bike and would like to reuse as much as possible.

Yes, though make sure it's a road compatible one (not MTB). I think SRAM do an Apex 1x flat bar shifter for about £25 that would work.

I emailed SRAM about this as I have a spare 1x11 Rival 1 mech.

I was told any of the current 1x11 MTB bar shifters would work with it.

Cheers, I’ll need the shifter anyhow