My son is 2,5 and to be honest, I'm glad to hear your GP said that they can live off milk until 3... That's a weight dropping off my shoulders.. We had the same but the underlying problem that came along with teething and other snotty noses was that he threw up.. Quite a lot.. Trying to wean him, it didn't make it better... He's only started eating properly and more than just a few bits since he was just over two, that's when he finished with all his teeth as they come one after another in brackets of about 2 weeks.
But he's 2,5 and he drained about 7 bottles over the last evening and night.. It's frustrating as he eats throughout the day, now naps at but I give him some dinner prior then refuses food when he wakes up.. I mean anything he won't even have a rusk or something nice cries for a bottle, has a little fit if he has too and drains my walled over night.. As he refused powdered milk from the minute he started having the littlest bit of routine with his milk..
I wouldn't start doing this until you're nearer the one but here's some things that helped us.
No more bottles before meal time.. When our son has has a bottle in the morning, say about 4-6 and he wakes up at about 8 he tends to want some toast about half an hour to an hour after. Depending on how late he still had a bottle. Water with a meal instead, my son needs some drink to have a swig during meal times.. It's not the best habit but anything to get them to eat!
Funnily enough, follow on milk or toddler milk.. Staging up the milk especially in the day, it has fewer calories and therefore it doesn't nourish as much as a stage 1 or hungry baby milk. This helped us massively.
Instead of spoon-feeding, which was a right nightmare with us.. Try bits that he can eat himself.. At the minute the only thing my son will wolf down is them carrot and potato waffles from asda and two chicken nuggets if I'm lucky.. I'd always blend loads of vegs in a soup or a tomato purree for pasta/pizza sauce..
Perhaps some offering things like french toast fingers, soup blended and dip some bread in then offer the bread. I would try some before a bottle is due but an hour to half an hour before rather than after. Offer some water in a cup he finds it easy to sip out along with it.. We did have food groups that does food sessions for weaning babies and toddlers although they have recently stopped these in our area.. It might be worth checking if your children's centre does a messy munchers group or something similar. It might just be worth offering the variety of foods, to get ideas and try them out. Also just try things out you've done before but maybe failed in the past, it may just not've been the right moment and re-introducing it again at later times might be positive response you didn't expect.
Don't stress yourself too much about it, it's hard but if you don't have a child that's persistently throwing up with every sniff. He'll go through phases where he might only want bread and biscuits but the good thing about it, it's only a phase.
I've also seen recently in a hospital/HV guide with weaning problems that when there's issues with weaning referral to speech and language might be required.. Now my son is late speaking which perhaps could be combined to why he's such a terrible eater along with why he so easily threw up now to me it totally makes sense because they do know a lot about movements and speech and thus are more likely to see if there's anything why he also has issues feeding.. Which might be an idea to think about if he persists to be a terrible eater once he turns one.. (The waiting list can be quite long). I hope my bookwork helps you find some ways to try and get some hope that it will and can get better!