That's definately not right. I'd say the mechanism is faulty. It might be worth checking with your local MoT station as it may be a fail point.

Either way, it's safety, so I'd suggest replacing the belt reel. Id personally have no qualms using a secondhand one off a similar age car (or newer), but I'd caution against spraying anything in the mechanism, you cannot guarantee the effect it will have.

Thank you, it has just passed an mot 2 days before I purchased the car from a garage

Presumably either at or paid for by the garage you bought it from????? in which case there's a VESTED INTEREST. Go to your local friendly test station and ask for an independant viewpoint.