In reply to Ciderslider:
Think it's possible to apply direct for assessment, or used to be, but you needed some persuading skills!
After training, you'll need to get some consolidation experience in your log book, which means it's going to be at least 2-3 months, unless you can volunteer at an outdoor centre - anything much less will be suspicious. People have been known to fabricate some/all of the experience, but they're not daft and you better be able to answer questions about it!