Once building is finished

[Teaandsugar]

What certificates should we obtain from the builder? Incase of any problems down the line? We had a part new roof, extension, plumbing including new boiler, electrics and structural alterations done. Building reg certificate is a must, but what about the rest?
First time renovation so just need a little guidance.

There should be certificates for the electrical work ( we had an extension and needed one for the building regs to sign off), new boiler would need one too. Unsure about any others.

Do the builders generally give a certicate on completion as a guarantee? and do we need one for resale or incase of issues down the line?

It should be signed off by building control.

As has been said you should have a certificate for the electrical work, a certificate for the gas related plumbing and a completion certificate from building control.
The builder does not have to give you a guarantee or certificate unless this has benn agreed as part of the contract.
As a builder I would not expect my final payment until building control have signed the work off.