So who do you expect to actually carry out this work ? There are companies out there but at a starting price of £59 per carb you aren't going to see much change out of £300 . And once they are back on the bike they still have to be set up . You say that you lack the confidence to do it yourself . So do it anyway , without any confidence . Read up , be methodical , be observant and gentle , stop if you haven't got the right tools , create a clean and well lit work area , put everything in little boxes like a pill dispenser and put the kettle on . This is how confidence is gained . . https://www.pccperformance.co.uk/collections/carburettor-services?gclid=CjwKCAiAlrSPBhBaEiwAuLSDUPWDgrJOAz2Hq3F1CMxdBgCiQ2snhp3LAEhecFkwR18hwid9AsMo_BoCvAkQAvD_BwE