Will be a difficult one to get around as most schools are geared up to do the brush ups with the max number of bums on seats to minimise costs etc. Having said that you could give these guys a call in Bournemouth as I know that they take on guys on a 1:1 basis. They are unlikely to do weekends though and I haven't heard of any schools that do.
http://www.gtserv.co.uk/index.shtml
PS: My experience of the brush up courses is 2 weeks (ATPL) and not 3 as you stated.