Thanks everyone who has posted. All your replies have been helpful, as I really wanted to hear from people who understood why I was upset about this.
Leoniesosleepy, thanks for that link which was interesting. I haven't read yours yet CMOTdribbler but I will.
PortandLemon, the link you posted didn't work for me - I just got the Talk index page. Can you post it again, or maybe give the URL? Thanks.
To clarify, because I don't think I made this explicit, I was already osteopaenic - it is not being suggested that BF has caused this, but rather that it is making things worse. Another factor I forgot to mention at my appointment, because I got upset during it, was that I had to switch from my usual blood thinning drug to a safe one while TTC and pregnant; the only downside is that the alternative drug has a bad effect on bone density. (Ah, the joy of multiple health problems...) So now I am back on my usual drug, the effect of 18 months or so on the other one should start to be ameliorated, I hope. I don't think it would have helped to mention this to my consultant, though because she (yes, a woman, somehow particularly disappointing) seemed down on BF from the start. She actually said 'well, after 6 months it's just for you, he's had all the benefit from it now', and I decided not to even bother arguing as she clearly thinks that and won't be shifted. In hidnsight, though, I am thinking of raising it with PALS at the hospital. She doesn't seem to have a long-term treatment plan for me as such, just said she would want a bone scan done at 12 months to see if density is recovering. The 18 month finding is very interesting in that regard, so I might want to argue for another / an alternative scan at 18 months.
I am just starting to try solids with my DS but he is barely licking the spoon as yet. I am also going on a 3 week trip abroad, visiting family, within the next week, so I have decided that I will definitely continue to BF through this trip, as there will be so much other upheaval for DS I wouldn't want to remove the comfort of his usual feeding routine as well. Afterwards, I may consider mixed feeding and try to reduce the Bf but without giving it up altogether, depending on how well he is doing with solids. But I will certainly not rush into ditching BF immediately or completely or necessarily at all.
Thanks very much all of you. I am feeling better now, at any rate.