sorry it's taken me so long to get back here, thanks so much for your replies.
i cant believe how sensitive he is to the taste difference, he is on neocate LCP so that uses diff oils to the neocate advanced, wouldnt be an issue if going from regular neocate to advanced i think.
we cant get banana flavour, only tropical which is a shame as i'm sure he'd take that!
anyways, went to see dietician. plan is trial yoghurt and then cheese as this is the easiest way to get extra calcium into him (no point looking at cows just yet since he is going off milk feeds). we are on day 7 of yoghurt, started 1tbs and added 1tbs every 2 days, he just had a whole pot today (4tbs) so fx, so exciting to give him something yummy! he hasnt had any dairy since 5wks old! if he goes ok on that then we'll try cheese.
now even with 1 serve cheese and yoghurt he still wont get quite enuf calcium with neocate LCP but will on advanced, so will try a scoop for scoop replacement of the formula (not too hopeful on this as think he will stall at 50/50). if no go then will have to look at other elemental formulas or flavoured neocate or a supplement. i can possibly get enuf extra calcium into him with other foods but he is highly sensitive to salicylates so is on very limited fruits and veggies and the ones that are best for calcium are to high in sals for him. but can look at chickpeas, egg, salmon, etc.
who would have thought being a mum would require being a dietician and a mathematician