In reply to GLUF:
I regularly make purchases under HMRC exemption self-certification. These are purchases of dedicated specialist communications items for a rescue charity.
The point of VAT, as the name suggests, is that it taxes where value is being added. This is true in any normal commercial operation where goods are purchased and then goods and services are sold at a profit.
In the case of charities and some public services, it is normal for there to be no added value therefore the HMRC tries not to make a meal of things and operate a tax system where it can achieve nothing.
If an ordinary shop or a property or facilities management company buys resuscitation equipment that will remain their property then they will pay VAT.
If a charity provides similar equipment for use at events or in a public place then, if the equipment fall within the correct category and the purchaser has self-certified the purchase, they will not pay VAT.
If an ordinary shop or a property or facilities management company buys resuscitation equipment expressly for donation to a qualifying charity then I believe that there is a method for exempting the purchase from VAT. I have no direct experience of the donation example.
Here are some HMRC pages related to this subject.
CHARITY FUNDED EQUIPMENT
http://www.hmrc.gov.uk/charities/vat/charity-funded.htm
CHARITY MEDICAL
http://customs.hmrc.gov.uk/channelsPortalWebApp/channelsPortalWebApp.portal...
NOTICE 706/1
http://customs.hmrc.gov.uk/channelsPortalWebApp/downloadFile?contentID=HMCE...
CERT E
http://customs.hmrc.gov.uk/channelsPortalWebApp/downloadFile?contentID=HMCE...