BYPASSING A GAIN STAGE - QUERY

[NGW]

Well, I just had a 'Light Bulb Moment' - thanks for flicking the switch Kevin.

I read your post again and looked at the schematic and the answer was there all along.
Relay 1B has contact #11 unused, which provides the means to select the output of Stage 1 or Stage 2.
#9 is already connected to Stage 1 and #13 is the input of Stage 3. 
I will connect the output of Stage 2 to #11; which will be a bit difficult, but it is quite doable and that should solve that.

The attached, revised drawing shows cct.

Thanks again, 
Noel