Here's a good...

Here's a good article:

http://www.aterwynne.com/files/web%20e-print%20aim%20glausi%204-07.pdf

It doesn't look like there is any minimum requirement in terms of sp. I also had a look at:

http://www.londonstockexchange.com/companies-and-advisors/aim/advisers/rules/aim-rules-for-companies.pdf

but couldn't see anything about minimum sp requirements. I guess it's up to the directors to nominate the capital raising amount and how many shares will be on offer. Then that would go to an AGM or SGM for approval?