Incorporation of a medical consultant

Client works providing medical eximanation reports for the police, gets paid per report and also a retainer each month. They do also provide some reports for hospitals etc if required. All currently under self assessment as a sole trader.

I can see no reason why they can't incorporate after doing research on the web. Do any of you know any different?

Also, how about a gp who provides out of hours medical cover on a fixed fee basis?

Many thanks in advance for your help.