Rolled out my own no-fiat service. What will the tax man need?
If you receive 500 EUR as a payment, how do you declare it?

Easy, you declare it as however much GBP it was at the time. If you receive it as a wire transfer your bank will even make this conversion for you!

So with BTC if you receive 2.5 BTC you have to see what the GBP value is and declare that as your receipts, and pay VAT and whatever other taxes on it.

Of course you can choose to lie to the tax man, but remember that Bitcoin is a lot easier for them to track than even your bank account, unless you are very good at operational security and you use something like Monero to separate your transactions. Obviously this is not worth it if you end up having to turn most of it into fiat to pay suppliers anyway.