They send us the forms about 3 months before the licence expires Alister so plenty of time to send them back - although you can now renew online. Mine was due on 28 June I think however because they looked at it whenever (April I think) my new licence runs from a date in April to the same date in June that it originally expired, in 2021. Doesn't expire at age 70 for me, as I only have a 'under 3500kgs' licence now.
If you have your C1, that would still expire at age 70 diabetes or not, then non diabetic you have to have a medical every 3 years thereafter anyway. If you are licensed to drive heavier vehicles, PSVs or different things, they each have their own requirements anyway, and all different from 'just cars'. I might still be able to tow more than you anyway cos these days you don't automatically get all the categories all us old uns did when we passed our tests.