Right the fault i had was the one way valve in the fuel pump had gone, so when i switched off i could hear a banging noise from the petrol tank where all the pressurised fuel was being forced back in, hence the pressure when you take the cap off!

Leave the car over night, and before trying to start it, gently push the metering flap down, there should be a little resistance, and it should rise slowly.

If there is no resistance and it springs back up rappidly and bounces etc there is no fuel pressure.

If you are not sure, you can prime the car a few times after and then press the flap down to compare.

I think you will find there is no pressure