Hi guys.
I'm posting this as hopefully it will save somebody wasting 2 hours like I just did.
Basically I just changed my sidelights and a couple of seconds after I turn them on, they go out.
First thing I checked was the sidelight fuse. It was perfectly fine. So I tried all my lights on the front to make sure it was just the sidelights. Oh I'd checked it wasn't just the sidelight bulbs by this point.
My dip beam was fine, high beam fine but no front fog lights and no sidelights and the green light on the dash indicating the fogs were on also didn't light up. I was starting to get seriously fed up by this point.
Checked front fog fuse, ok, relay was perfectly fine.
I searched this forum and others and all the info I could get was its the relay but mine was fine so completely stumped.
Then just out of curiousity I checked the rear fog lights. I hadn't thought about the rear lights as i was sure it was a front end problem. The rear fogs worked fine but I noticed I had no tail lights. Pulled the tail light fuse and it was blown. Replaced it and hey presto I have all my lights working again, sidelights and front fogs.
What I can't understand is why are the tail lights, front fogs and sidelights affected by the tail light fuse? Front fogs and sidelights have their own fuses! Strange one but just glad I got it sorted :)