You have two battles to fight...
One is with regard to your visa status and residency. In theory, there is no reason why a college should not take you on as a student in any subject. As you have not been in the UK for three years yet, and don't have ILR, then you will have to pay international fees.
The other battle you have is with the new NHS regulations on the employment of overseas national medical professionals. I think you would probably be better off posting in the 'on the job' section to get info on this, but basically there is a freeze on the recruitment of non-EEA nurses (other than senior level) into the NHS. This might have trickled down to nursing colleges and there may actually be a freeze on even letting people study to be nurses!
If you do a search and find Alicia, she is a nurse in London and will probably have much more info.
Vicky