Once fully developed, I could be persuaded to put the entire design onto a single PCB and if there is enough interest have this made commercially and make PCBs available.  This would be subject to the following caveats:

There will be no RF LO, you'll need to do your own 4X input signal, from a crystal oscillator, DDS etc. 

Output filtering is not included.   The use of a switching gate mixer means odd order harmonics of the RF LO are very strong and must be removed with a low pass filter appropriate to the band of interest.  I could place pads on the PCB for filter bread boarding.

Construction will be in SMT - I use nothing else, and haven't done  any wire-ended construction now for nearly two decades.  So you'll just have practice SMT soldering and accept the facts of life.  All the ICs are basic  SOIC devices with 1.27mm pitch, and components are 0805 or larger, so even the "older" constructors (like me, now, I guess) should be able to manage them.  In fact, even those SOIC packages themselves look a bit dated now compared with the TSSOP and QFP packages I regularly use.

In order to gauge interest in   a) bothering to lay out all bits on  a single PCB, or b) having it made commercially, could I get an idea of who / how many would be interested.  Please reply directly to me to avoid clogging up these groups unless you have comments applicable to a wider audience.   I just want a feel if it would be worthwhile.   

It will be several weeks before things are finished and written up, and then another few weeks for PCBs.  Cost each will be consistent with all other PCBs offers of similar size - I use a professional good quality UK based supplier, and don't try to cut costs on cheap Chinese PCB manufacture; however good others claim they now are. 

Andy  G4JNT