Currently 2L (subject to change)
London Gatwick, Edinburgh, Bristol, Aberdeen, Teesside, City of Derry, London City (some lanes).
Still 100ml
London Heathrow, London Stansted, London Luton, Manchester, Birmingham (mostly), Glasgow, Belfast.
Always check before flying
The UK DfT has previously reversed 2L allowances at upgraded airports with minimal notice. Treat 2L as a bonus, not a guarantee.