I don't think you can get it on prescription here in the UK because it isn't licensed.
I ordered mine from Biovea, it's about £40 for two bottles (50 20mg applications per bottle) including delivery. Takes about a week to arrive as it comes from the US and was the best deal I could find online with the fastest delivery. Everywhere else seemed insanely expensive in comparison.
It was excellent initially but my two previous cycles it hasn't been. I found my temps were higher and my anxiety lifted at first, but this didn't happen with my previous cycle - my temps dropped hugely after 6dpo and kept lowering despite me using 200mg of the cream daily split into 12 hour applications. Cycle before my temps weren't particularly low but my anxiety was there constantly and my temps were rocky. I swapped to Cyclogest pessaries at 10dpo previous cycle when my temps kept lowering and my anxiety wasn't going anywhere and they were amazing. My temps increased nicely and my anxiety disappeared.
To be honest because it's hard to get and because you have to wait on delivery for ages and the expense of it, and the fact it seemed to stop working (I think it gets saturated in fat tissue and gets stuck there eventually, isn't meant to happen when you alternate areas but it's the only explanation I can find for it not working), I would ask your doctor for a licensed form of progesterone instead.
Pessaries you can use front or back door (front is generally advised I think but back door is advised for those who suffer frequent UTIs but this can give diarrhoea), they can irritate you a little but I found drinking plenty made this go away, they come in 200mg or 400mg and I think it's more logical to space them every twelve hours instead as progesterone starts to drop after about 12 ish hours.
You can also find it in gel pessary form, injections and oral tablets (which can be used vaginally). The oral pills aren't as good because they have to be processed by your liver which means you're more likely to experience side effects from them. I think this is why some women use these vaginally, that and the fact apparently it's been shown to work best this way anyway.
The creamis good for some people and I have read countless glowing reviews on it but it only worked temporarily for me. When you think when it's used to support a pregnancy early on, if you conceive you have to stick with supplementing until about twelve weeks gestation until the placenta takes over the production of progesterone, so if you use cream and it does the same to you as it did with me, and stops working after a while, this may cause a miscarriage. The other methods of delivering the hormone don't risk getting stuck stored up in fat tissue, so I think are more reliable