The costs of a hotel room or B&B accommodation is allowable for overnight stays while on business. There are no defined limits on the amount but it must be "reasonable". The circumstances and distance must make it "unreasonable" for you to be expected to travel home.
For longer periods working away from home it might be cheaper for the business to rent a room or flat. Renting a room or flat is only allowable as a business expense where it is not the principal residence.
You must: Remember the 24 month rule applies to any claims. Have a receipt for everything you claim.