OK - after some faff, and lots time..
I have exported the geo-referenced jpg files from that spanish map site - 1:50,000 tiles. for areas covering RB1 and RB2 routes.
I then used a bit of free software called SAGA!!!! no not sliver head holidays - but gis programme
http://www.saga-gis.org/en/index.html
i then loaded all the tiles into this - did Rb1 then RB2
the software is a bit anal to use, but works.
i work in a software company so geological interpretation and seismic - so used to this type of challenge....
the problem is it splits the jpeg into 3 component colours, Red Green Blue = RGB
so first i had to recombine each RGB map. using the grid command: Grid>visualization>RGB composite
then i used to merge function (Grid>construction>merging) - that took some tweaking of the parameters to get it to work correctly,
you need to set then interpolation option to "nearest neighbour"
and overlap mode to "first value in order of grid list"
but in end it did an excellent job of automatically stitching the 15 individual geo referenced jpeg into one file.
then i exported as a "true colour bitmap" - it creates a *.bmp file and a *.bpw (identical to a *.jgw file)
(i tried the export option to jpg - but the progamme threw a wobbly)
i was then able to load into my GPS Utility programme.
i then exported a waypoint from GoogleEarth and imported into GPS Utility - and discovered there is a discrepancy of about 150m. which i will either live with, as its a consistent shift in a NE direction
or i can recalibrate using the Googleearth kmz waypoints
i will see how it tallys with the RB1 and RB2 gps co-ords first when i have bought them
but job done!, not easy, but got there in the end - the slowest part was exporting all the georef jpeg from the spanish website