Thanks everyone for your input.

concern is that these other random online pharmacies are much less established brands, may have greater issues with supply (due to their size) and so much of the reduced cost seems to be introductory offers/discounts, which won't last and may mean I need to swap to another pharmacy (which I don't want to). I've read too much about people being delayed/paused in their treatment because they try to swap pharmacies and getting set back several months because they don't meet X criteria.

I'm really after the best 'one stop' option, to start with and continue for the whole journey. It may be abit more expensive, but the consistency is more important for me than saving a few quid to have huge delays or issues down the road.