I have had similar problems with HMRC
You could have a board meeting to qualify that the aircraft is not available for private use only company business ???
To stop BIK totally. you could get your insurance company to state either no private use , only private use with specific board permission
The HMRC can't charge you BIK if the heli is not insured (not legal to fly ) and the aircraft is not available to you 24/7
Been there done it paid for the tee shirt