Most likely "carro". (I've seen it used in TV ads here in So. California.) Here's a link I saw on another thread: http://www.woodwardspanish.com/how-to-say-car-in-spanish-coche-carro-auto/
Well, I'd imagine as with most expats they'd be concentrated around London but I live in the middle of nowhere in Wales and I often hear people speaking Spanish and Portuguese on the bus - come to think of it often Portuguese but not very often Spanish. Have you tried http://www.meetup.com ? They have social groups made up of people with (usually) one shared interest. I use it for French speaking 'meetups'. They have groups in various towns and cities across the UK (and the world) so no guarantees but if you live in or near a city there's probably a Spanish meetup group nearby.