Yes, certs are expensive, but sometimes needed to verify what we have found, best to be sure 'before' you go further back that you are on the right track.
There are alternatives though. For marriages, if you can identify the church and date you can usually get a copy from the parish register microfilm at the archives, which is about as authentic as it comes. Its the source document , the one that was written at the time of the marriage so will have the good stuff like original signatures. Once I have the right info, I order them from the archives. a photocopy from a microfilm costs about £1 plus postage (no postage if you can go and collect them, but the postage probably works out cheaper than petrol if you aren't really close to the archives) so lots cheaper than a civil registration certificate at a minimum of £9.25 a go.
Church baptism registers sometimes (though not always) give birth dates as well as baptism dates so they are a good substitute for a birth cert.
Burials, again 'sometimes' give dates of death, but usually, if its not in my 'direct line' I settle for knowing when they were buried, as they will most likely have died within a few days of that and I have to budget for my hobby, as we all do.
Boo