Series 3 MOT Issue

I have a series 3 88" hardtop. As most of you will know there is an issue with vehicle weights declared on V5s. Mine says (like everyone else's) 3499kg....which it is clearly not!
I spoke to the DVLA and they said send a rubbing or photo of the VIN plate and they will change the V5 accordingly.
My VIN plate is blank! What do I do? Own up? stamp it? Does anyone know the legal position. I spoke with an MOT centre and he said don't worry - he would still MOT it as normal......but he may not be there next April when it is due! Help please? Thanks.

if when the mot station logs onto your vehicle and it does not give a kerbside weight (which last time i tested a series it did not) the station has to resort to the old method of brake testing ie. the brake decelerometer test on the road.