I'm not sure how £1000/day even makes sense. Isn't that like £20000/month, which computes to ~$400K/year? What am I missing? Is it only part-time because of consulting?
It's was for an investment bank, full-time 6 month contract, they were looking for someone who was strong at multi-threading and networking, and could be a lead dev. That's a rare enough combination of skills.
I'm actually trying to bootstrap my startup, getting people waving wodges of money in front of me to do contracting work instead is really distracting :P
Typically you get to keep more (generally 73%-75% of the amount), but you'll also need an accountant to minimize your taxes and that'll cost you about a grand a year. But in most cases it's worth it.
