I checked my settings with another posters suggestion and found my setting was wrong.
This is what I did:
click start
Type 'services' in the search bar
Select services along side the 'cog' icon which should appear.
when the window opens and the right hand pane populates scroll down to Windows time and click on that item.
check what it says under the column 'Startup type' (mine was set to manual for some reason)
in the menu options select action and scroll down to properties.
Now under the General tab there is an option to change the Startup type to a whole host of things. I changed mine to automatic and it worked ok since (well for 15 minutes anyway it kept up with the time on this website:
http://www.timeanddate.com/time/zones/bst (but you may need another website to check if not working to BST)
Its worth noting here that the other poster who directed me to this setting suggested choosing disable rather than automatic. They said it worked for them.
Good luck