Let's say I invested �3000 in a stocks ISA in a nominee A/C and sold at a profit, making the total now �10,000. The money stayed as cash. If l buy another share, in the next tax year, I assume the rules will not allow me to invest all the �10K in an ISA as it is over the limit? Or is the profit considered to be part of the original �3K?
If you sell the shares and take the money out then it becomes new money again for tax purposes. You could leave it all in the ISA wrapper though provided you buy other shares, unit trusts, bonds etc- but not cash.
This may help: http://www.creditchoices.co.uk/partner-lp_share-isa/share-isa.html#8