You live in the UK and that's a provider there. There should be reviews on the company somewhere on the internet. If Your Health Care Provider recommended the company it should be a good one. :)

I've never used it, but I've used something similar, and it can help increase your respiratory muscles and get them in better shape. Regular exercise will do the same thing. As for the "flutter" idea to help bring up mucous, that's similar to a variety of different devices available in the US. Some people swear by them and others don't have much luck. Bottom line, this device can't hurt you and may very well be beneficial to you. If you're really interested, give it a try!

what is Aerosure medic?