Hi Donald, I too display my tax disc in the same place as yours and you are right, you must display a current tax disc.
I once got done by DVLA £330 for failing to display a tax disc, plod were not bothered as all documentation was present and correct, tax disc was in the post from DVLA.
No amount of ranting and letter writing would sway them though, pay up or we'll take you to court at your expense.
Heads they win tails you loose.
