1753 is no longer in platform 2 dock at Sheffield Park.
It may or may not still be on the railway - I don't know.
I do not believe there would be any space on the Bluebell to form the work base of a restoration group for 1753. Platform 2 dock is shunted regularly as a base for operational stock to be stored in the short term. It's possible the 9F could be moved, but where to, I do not know.
All platforms at Horsted Keynes see services trains from time to time, regularly on 2 and 3, and occasionally on 1 and 4. Both are needed constantly as stock storage.
Space is especially at a premium at the moment as many of the up yard sidings at Horsted Keynes are lifted and/or unavailable.