UK - travel insurance

I'm trying to take out annual travel insurance (I live in UK). I have declared MS on there and there is a follow up question about if I am recieving / waiting to receive treatment for this. When I select I am waiting to receive treatment, I can no longer take out insurance - this is through Compare the Market.

Is Ocrevus/Kesimpta waiting list applicable to declare on travel insurance? Or is that for disclosing things like chemotherapy?

Also, once on the treatment, do you declare it and is it still simple (just slightly more expensive) to obtain travel insurance? Or do you have to go through specialist travel insurance

Thanks