It appears that a US trend has started to catch on in the UK with teachers now looking to sell their lesson plans to other teachers struggling for ideas. The idea has become so popular that the TES (think, educate, share) website has set up a specific members only buying and selling page.
The resources that have been uploaded are fairly inexpensive at prices around £1-£2 per lesson plan however if you could sell that plan to a large number of the current 3000 members then you could have yourself a nice little earner. The only thing that you need to be aware of that some schools consider school lesson plans to be property of the school so to avoid conflict it could be an idea to discuss with your head teacher before selling any of your lesson plans. It’s also worth remembering that any money raised as an additional income would need to be declared to HMRC and could be taxable.