Hopefully this info will help others who need to do what I've done today.

Horn packed up on SWMBO facelift HSE so first check was fuse - OK; then relay - OK; so, that left horns themselves - not OK.

Searching online found the LR part number (LR040705) & from that got some pics which enabled me to determine they were FIAMM units. A bit more searching around & managed to get a set for £28 - £20 less than the cheapest I could find the LR boxed set. FIAMM kit is AM80SX (see pic below).

Unfortunately you need to remove the whole bumper to get to the horns but removing them once accessible is a case of unplugging a single plug then two 10mm nuts. The new FIAMM horns come complete with the correct connections & new nuts so fitting is quick & easy!

The hardest bit is removing the bumper & refitting it... but that needed to come off anyway to fix the faulty parking sensor but that's in a different thread!

Thanks - good to know - more nuggets of information to be stored away for when its needed. Jules