If you are getting the same result on both Ancestry and FindMyPast, (though they don't have the images for registrations that recent), then I'd guess that what you are seeing is what is in the GRO index.
I am not sure if the index, for such a recent event will be available in libraries (but am obviously wrong as davidft has posted to say as much)
The GRO index, like any index will have some errors and I'd suggest that you contact the local registrar (some local registrars will reply to queries, others just say to buy the cert as a default) , succinctly give the reason for the query and ask if the register can be checked. NB just give the year and quarter of the event as local registrars do not use the same page and vol number the GRO do)
If its a birth and your query is in connection with a MMN, just ask if the registration is a match for the MMN you think it should be,
If its a marriage and the spouse's surname is your query, ask about that, but do bear in mind that people do re-marry and the registration may be in either the spouses birth surname OR their previous married name
If its a death and its the age that you are querying, again bear in mind that the information in the index depends on the knowledge of whoever is registering the death and may not agree with the actual facts.
Other than the above, your only option is to purchase the certificate and then, if needed , retrospectively complain and tell them you want a refund IF the info on the cert does not match with the registration details (NB just say you expect a refund, if you ASK you are giving them a choice to refuse - start from a stance that says - you have incorrect info online which has caused me to spend x amount I didn't need to. Asking, however politely, gives them the option to say no)
Boo
