Just realised I didn't update on this,
Well we took Milo and the vet didn't understand why we were told to bring him down so she didn't charge us for a consultation, (bless her) she wormed Milo for us, we have to do it once more next month, then she did say once a year will be fine for both of them.
I asked about his size and she said his fine not underweight etc, but he has finished growing and we have a tiny adult cat, bless him his always going to be a mini milo.