M Reg, 1.4 alpine. l drove approximately 80 miles, as l came to a roundabout off the motorway, l went to down gear and it would not go into any gear, l tried to force it into 2nd and it made like a grinding screeching noise. l had to roll to the nearest pull off. l turned off the engine thinking it had overheated or something, and 10 minutes later when l started my engine it was working again, but in idle mode it was making a squeaking sound just about audible through the engine noise. any ideas as to what could have caused this and what further damage it has caused, and what l should do?

YES.
Your gears will not change IF YOU CAN'T disengage the clutch disc from the flywheel. In other words, ur ''release bearing is too old, & has worn down to a thinner size, it cannot push the clutch spring hard enough to disengage the gears. And / or ur clutch driven plate is also too thin.
Your gearbox has to be ''out of gear'' before u can change gears.

Later, when the engine cooled down a bit, u could do something. This wo not last much longer. When nothing was spinning, u could get back into neutral to start up.

The high-pitched sound is the worn out bearing again, spinning at a high speed,and it makes noise.
l promise u this is the problem.

Time for a new release bearing (throw-out / thrust bearing) & while the engine is open, a new clutch spring & driven disc.
This is a last warning from ur engine. If u wait longer, the remaining clutch surfaces get very hot & cause a loss of steel temper of the flywheel. This leads to ''out of perfect flatness & trouble = vibration.