Apology accepted Neil and for what it's worth I share your abhorrence of the mindless application of the letter of rules by bureaucratic jobsworths. I (and my brother) also share your distaste for tax on tax, which also applies to the fuel duty on petrol and derv. Sadly neither he nor I can alter the simple fact that politicians have chosen this devious route to raise revenue by stealth. That is not interpretation it is what was intended.
Sending you a bill for 5p (or even £5) is however ludicrous as it costs more to administer than it raises in revenue. That comes down to failure to build safeguards into the system that prevent the sending out of bills that cost more than they raise. The fault of both those who designed the system and those who specified and approved it.
My main point however was not to defend the revenue but to reinforce your warning that care is needed in what is written in open forums. You never know who is reading what you write.