Hi Popeycymru. I rode to Barcelona from Le Harve in 2006 & 2008, & from Milton Keynes in 2007 (always finishing at friends in Majorca via the Barcelona ferry).. I pre-plotted the route in Microsoft's Autoroute to get the ball rolling then purchased IGN maps (Institut Geographique National) from the hertford map centre, but I think these may have changed, these maps are intended for cycling (1:100 000) scale (1cm = 1km), I purchasing about 8 of them for the entire route (2006 & 8) & marked my intended route before leaving, best contact the map centre to find out, unless you're into SadNav, sorry, Sat Nav. I rode it in 10 days, aprox 80 miles / day.
I basicaly went Le Havre - over 'le pont de Normandie' bridge which is an amazing thing (speaking as an engineer!), Le Mans, Tours, Toulouse, Pammiers then over the big hi!! into Spain via Bourg Madam. Two passes, first is Col de Puymorens @ 1915m (France), then La Collado de Tosses @ 1800m (Spain)
I'll dig out further details if you are genuinely interested, pm me if so.
Mark.