There are now many websites with very useful educational materials. You may want to search using key words/phrases for example 'KS2' or 'KS3' so you can focus on UK resources. Your school will have lots of websites they use on a regular basis. If you find anything really useful do let me know as resources are continuously being updated.
London Grid for Learning
This is a Consortium of all London LAs working together to put in place high quality online resources and services for schools. Some areas need a username and password but many London schools will have automatic access.
Here is a video explaining their work by Michael Rosen if you want to know more. http://media.lgfl.org.uk/files/content/2011/primary%202011%20content.wmv
This site has lots of practical resources and good ideas to use in the classroom.
This site has lesson plans, activity ideas and resources for primary teachers.
Interesting Teaching Ideas
This is a collaborative website with lots of great idea.
This site has teaching ideas for primary teachers.
Ideas to Inspire
This website is one of my current favourites with lots of good ideas and resources for all teachers.