Glad it is sorted .
This pearl of wisdom sums it up for your Bil or indeed any other sinner.
This should take you directly to the page for paying fines without a digital signature:
https://sedeapl.dgt.gob.es:7443/WEB_Sanciones/jsp/sincertificado/identificacionPagador.jsf
but you will have to allow security exceptions.
There is a help page here:
https://sedeapl.dgt.gob.es:7443/IWPS/help/sincertificado_en.html (in English)If all else fails try making the payment in a Bank of Santander. This is the bank through which you can pay in Spain but I am not sure if the facility extends to UK branches.
Kevin - Happens on all the Spanish Government type web sites...I'd be more concerned if they came up "clean"... ;

Spain may look third world in may areas but it is pretty hooked up on computing. Just two examples. Repeat prescriptions. You just go to a Pharmacy in your province and show them your health card and pay. Have an accident or visit a different doctor and hospital and your records including Xrays, treatment is there online. Mind you to let the side down, some banks only allow payment of council tax between 9 and 10.30 a.m. The mind boggles.
Anyone holidaying in Spain . - Like Britain they have cottoned onto the
money making safety possibilities of speed cameras. In fairness they publish the positions of fixed cameras. sat nav devices (well ours anyway) are not at all reliable. A 70 mile stretch i go on tomorrow has THREE but Tom Tom only knows vaguely where one is. It also isn't accurate on the speed limits.e.g. it thinks an 80 section is 100.
If you hire a car in Spain, any speeding fines are usually paid by the hire car company via your credit card once you are back in the UK.