No it didn't come with a receipt or certificate, and I don't think it's possible to get an appraisal for jadeite in the UK.
I had no idea that fake jade existed until I decided to do some research out of interest, and found that my bangle is type B+C, essentially fake.
Type A = Natural, untreated jadeite.
Type B = Soaked in a strong acid solution (the "B" comes from the directly translated "acid bath") followed by bleach to remove impurities and wax to make the surface appear shiny. No dye is used.
Type C = Dyed jadeite, but the way this is done actually destroys the internal structure of jadeite and the dye is not permanent.
B+C = Both acid treated and dyed. Capable of producing some gorgeous looking bangles, but they won't last long.
Technically types B/C/B+C are still jadeite, but without undergoing these treatments their quality would be regarded as trash, so as far as most people are concerned they don't count as "real" jadeite.
For practise & research purposes I went on ebay, entered "jade bangle" and the number of sellers flaunting B/C/B+C as A is unbelievable. Sure there are a few type As, but many of those photos are either photoshopped or shot in ways to enhance the look of the bangle - if you were to purchase one, you'd undoubtedly be disappointed with what you receive.
Also, apparently the prolonged wear of treated jadeite can be harmful, because they've been exposed to so many harsh chemicals. As the dye fades and coating wears off over time, some of it will be absorbed iby your skin
I'm by no means an expert; I've only been reading about jadeite for a few days and have barely scratched the surface. But if anyone's interested, I could translate an article I found which lists a few of the characteristics of treated jadeite.
Thanks, Storm Spirit, for the education. I am actually very interested, if you wouldn't mind translating the article (from Chinese?). Luckily, I had most of my pricier jade pieces examined by a gemologist and was relieved to find out they were the real deal (not dyed/treated). What I would suggest, when purchasing jade represented as natural and not treated from a dealer, insist they write on the receipt that if it is discoved otherwise, the jade is returnable with full refund. If they refuse, I would not purchase jade from them. I've found that this always worked for me.