Well the rafters are OK https://www.timberbeamcalculator.co.uk/en-gb/span-table/rafters?load=0.75&class=C24&plasterboard=1
And BCSA Blue Book would indicate that for a 3m span, with a 6kn/m run loading, is more than adequate. You will just have to trust the SE
And BCSA Blue Book would indicate that for a 3m span, with a 6kn/m run loading, is more than adequate. You will just have to trust the SE