IR35 is unlikely to be a problem, as you are being paid directly as a sole trader, rather than through an intermediary (usually a limited company). Whilst your status may well be an issue, your employer would be more at risk than you.
The only way I could do it is not work full time and have other clients as well.
That is not strictly correct, it's only part of what you'd need to do; it's rather more complicated as I said in my recent post. But he's certainly right that you wouldn't get away with being self-employed if you are working for them 9-5 Mon-Fri.
If you're planning to move away then I wouldn't try and change anything at this stage. Make sure you complete your first year with them as this gives you some employment rights, should you need them.
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JohnG
Small Business Guide to Employment: April 2008 update now available at www.garnerharris.com
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