Re: £300bn annually to the economy?
IT Contractors UK had this to say on the subject:
There are approximately 2 million self-employed professionals working in the UK. Out of which, approximately 1.77 million working as full-time contractors and about 234,000 working on a self-employed basis as their second job.
Number of self-employed professionals in the UK has increased by 43% approximately. The overall contribution to the UK economy by freelancing professionals is around £119 billion.
I think that's a more believable number. I would point out however that these 1.77 million people are not all about to stop working and the revenue will continue if they go permanent, so to say "worth £300billion to the economy" is bullshit.