Most toilet basins have a couple of wingnuts on either side, around the back. Its common for these to come loose over time.
Try tightening them from underneath, with any luck, you should screw the up without the need for tools.
I had a toilet seat like that, Tamaris. It was hard to stay seated when it shot me sideways so I had the chaps who fitted the bathroom come to fix it.
Shortly after I was having a drink in the local pub with friends when the bathroom fitter came through the door...saw me and shouted across the crowded bar......Hi, Gness......I trust you're not falling off the toilet any more..... :-(
We had that problemand no matter how we tightened the fixings suddenly the toilet seat would shift. We had to advise visitors that "the toilet seat is on the move again" - how bad was that?
In the end (no pun intended) we bought a new removable seat. It is brilliant for cleaning purposes and it never shifts. Might be worth considering.
I've had a good look under it and found the bolt. I've tightened it. There is glue though on the top so I thought that was the problem. As you can tell
I'm not a diy enthusiast. Thank you all.
Can't really understand the set-up here, but I'd recommend an epoxy resin like Araldite for it's strength and water resistance. should last another 8 years at least!