Cats and heat-advice needed

Hi all,

I was just wondering about your opinion of how cats handle the heat.
Curently in London is over 30 degrees C, so exhaustingly hot. They are
pretty much indoor cats, but do get access to outside only on the leash and
harness. However on this heat, I'd rather not let them out at all.

I know cats often sit on the sun and love the heat, but this is quite
excessive now, and with all that furr, I wonder if it does bother them.
Should I be giving them a shower/bath to cool them down? What do you do on
this kind of weather?

Thanks

Gee