Hi
i was given Eumovate cream at one time to use on the vulva - i used it for 3 months before going back to see a consultant. It is a steroid cream which is meant to reduce inflammation - sounds similar to Betnovate you have for the urethra and i agree is probably too strong and may well be causing more irritation.
Vaseline was suggested to me by GP as a urine barrier - i used this for some time also but found that it mixed with the white fillers that come out of the vagifem - my vulva skin went quite greyish and matt in appearance after a time - i probably used it for too long. I think vaseline is too cloggy for skin down there.
Another doctor recommended Emulsyfying Ointment to use a teaspoon full with a little water to wash with when my vulva skin was looking quite red - this sounds similar to the Aqueous cream which i haven't tried.
On another forum i found that Waitrose baby bottom butter - think that is what it is called - had helped - it has natural ingredients in it like olive oil. I found that it irritated more.
Also tried vitamin E oil squeezed out of capsules after a forum read but gave up on that as well !!
i read somewhere before about your burning with sitting - could i suggest that you look up Hope Pudendal on goggle that will take you to a website that on the left hand side has a symptoms button that will take you to a page that explains Pudendal Neuralgia. Pain on sitting is a symptom of the pudendal nerve being irritated and may be the reason for some burning.
A physio recommended drinking at least 4 pints of water a day to dilute the urine, washing with a squirty water bottle filled with water or getting in the shower after urinating especially the first pee of the day which is strong or even peeing in the shower. I too have stopped drinking tea and coffee to avoid tannins - gynae suggested this.
Sorry this has turned into quite a few negatives but what didn't work for me may work for you.

Hattie X