Bob Eager wrote:

Plusgas, as stated. But not WD40 - not really designed for that. WD40
is a water displacer, and Plusgas is a 'dismantling agent' or some
such.

WD40 is suitable, I've used it many a time for this application.

From their website;

"PENETRATES: WD-40 loosens rust-to-metal bonds and frees stuck, frozen or
rusted metal parts".

I seem to remember a Which test report that confirmed this

--
Dave
The Medway Handyman
www.medwayhandyman.co.uk
01634 717930
07850 597257