I did a stupid thing. I managed to screw up the design of this incredibly. Well done me. The sweep vs frequency is the wrong way round. Also the linearity of the sweep was terrible due to the circuit loading changing with voltage. This is a combination of rounding at the extents of the sweep and the inability to integrate any kind of network to fix the varactor non-linearity resulted in scrapping it as well. Straight in the bin and back to the drawing board.
Ergo I sat down this afternoon with Tektronix sweep circuits concepts book [1] and did some thorough research on Miller Integrators and came up with the following which actually works nicely when loaded and is easy enough to gate plus it's dead simple!
I'm going attach the existing sweep scale and offset circuit and then a diode clamp network to trim the linearity. You can then disconnect the input stage, apply fixed voltages from a precision power supply and trim each for stable voltage vs frequency. Looking at the linearity required, a total of 8 networks should be required which isn't terrible.
Also got to play with my freshly restored Tektronix 475 so a happy evening
Also found an excuse to buy a pulse generator!
[1]
http://w140.com/tekwiki/images/a/a4/062-1098-00.pdf