You can save a lot of money doing the work yourself.
We paid £100 pounds for a builder to come in and install the beam, then knocked down the wall and disposed ourselves (we were doing other DIY work so had a skip), I arranged the building control sign off (£150ish 5 years ago) and bought the beam (£100) and we did the fire protection and made good.
We didn’t require any calcs, building control came round before we started work and confirmed that they wouldn’t require calcs if we installed a beam of a X size with Y size bearers.
We had quotes for £1500 for the same work all in.