Help! Is there a law for tyre/rim size/tubed tyres?

Hello all, i've searched but not found anything yet that helps me.
I had a blow out on the defender which is running 265/75/16 tyres on a 6.5" rim with a tube. I went to get a replacement and was told that it was illegal to have this set up and the shop (an indy. land rover specialist) refused to fit the tyre/tube as they claim the landy shouldn't have passed an MOT like this. so im left with a wrong sized spare on one corner which obviously isn't good!
Does anyone know for certain if this is illegal or just not recommend? because I need to get this sorted as I only have the landy for transport!

Thanks in advance!

Taggy

A tyre that size is recommended to be fitted on a 7 to 9 inch width rim There is no reason not to fit a tube if you wish , I would advise that if running with a tube, then you need to make sure that any labels , stickers inside are buffed off , esp the glue residue which will be damaging to the tube, and cause a puncture later on . Certain 6.5 rims are due to construction not suitable to run tubeless. A 6.5 rim would have had a 7.50 or 235 section tyre originally .

Many thanks for the reply! I went to a different place and got a tyre fitted. Ifeally id like to put 235's on but one tyre was cheaper than 4! It has the old rrc wheels I believe at the minute. Think I may get modulars so I dont need tubes eventually.