carlston49:
It looks like the home office allowance that LTD drivers can claim increased on 6th April 2020 from £4/week (£208/year) to £6/week (£312/year).
If you use a room solely for the business you can claim a percentage of the mortgage interest/rent/gas/electric that that room is of the property so if the property has 4 rooms and you use one purely for an office then you can claim 25%.