Hi Theresa,
Yes I believe that what Gillian and Robert already confirmed is correct, and there's no way you can see a certificate before buying it - not England and Wales registrations anyway (not sure about Scotland). The best chance of confirming any information before you buy it would be, I think, from the Local Registry Office which covers the town where the event was registered.
On several occasions I have written to Local Reg Offices enclosing my cheque but telling them I'm not sure whether I have the correct index entry - so please could they check it first - eg - if it's a death, give them the approximate age, possible address the person lived, names of relatives who might have been present at time of death. If the details they have in their register doesn't agree with that info, they have always returned the cheque to me. But that's me posting from within the UK, & I suppose its a bit more tricky if you're overseas like yourself. But what you could do is - email the Local Registry Office (not the General Registry Office) and give them as many details as you can, and tell them you want to be sure you have the correct entry before ordering the certificate. Worth a try?
Carole