Do you wash the meat/ minced meat before cooking?

Nope, unless you eat your meat raw there is no need, the temperature you cook meat at is high enough to kill anything but gone off meat and is far higher than the temperature of the water you are washing it with.

That said I'm in the UK and we don't have things like chlorinated chicken...

You shouldn't wash meat as a general rule. You risk spreading any bacteria around the sink and work surface and increase the risk of cross contamination. If you cook meat properly you kill any harmful bacteria.

I cook straight fromt the packet. The first thing I do is sear the minemeat regardless of recipe so nothing going to survivie that !