Hi Jon. I sent your message onto
Practical Motorhome's Gentleman Jack, who responded as follows:
"Firstly let me clarify the position.
I’ve assumed that your wife currently has Group C1 on her licence. She will lose it on reaching 70 years of age. She can apply to retain it and providing she passes a medical and has no serious on-going notifiable medical conditions, she can retain it without having to take an additional driving test. The medical prioritises corrected vision and she will need sufficient vision in both eyes. Corrected vision means that you can wear spectacles or contact lenses for the test. Your GP surgery should be able to arrange a medical and costs are really down to each practice. Some don’t charge at all for registered patients, other NHS doctors charge up to £200.00. There is an organisation which advertises that it will arrange a private medical by approved staff at a clinic local to you. The charge for this is £50.00. I’m pretty sure they will also advise on the paperwork (
www.d4drivers.uk). Finally any entitlement to Group C1 over the age of 70 is likely to be for three years ... after which you will need another medical. Some with on-going medical conditions may only be offered a one-year extension.
To down-plate a vehicle that has previously been up-plated is a relatively simple matter. There will be a metal VIN plate under the bonnet or in a cab door jamb giving four weights the first of which will say 3500kg. This will be the original one and the one the DVLA/VOSA may wish to see a photograph of. When it was up-plated the company responsible should have fitted an additional plate nearby with the first weight showing 4000kg (or 4005kg). This has to be removed and the DVLA/VOSA may ask you to send it with your correct form V5C (‘log sheet’). Form V5C contains instructions on how to get it altered. Don’t forget to inform your insurance company. This is a legal requirement, but in addition you may get a small extra discount at renewal time.
Note that any driver must have the correct licence and be insured to drive any vehicle at its plated MAM (Maximum Authorised Mass) or what used to be called MTPLM (Maximum Technically Permitted Legal Mass), not what it might weigh at any given time."
We hope that helps!