Does anyone know how many cavers roughly there are in the uk/britain and how many are members of cave rescue teams.

thanks in advance

Here's a previous discussion for starters: https://ukcaving.com/board/index.php?topic=21184.0

Very much depends how you want to define caver (& who you consider to be team members)...

My educated guess is this...

There are about 2000 active cavers (those who go regularly as their sport)
There are about 6000 members of BCA which is made up of nearly all club cavers
There are about 12000 people who might call themselves cavers although many of these will be inactive
There are about 150,000 people who participate in a caving activity each year on an instructed trip

For cavers read people who explore or are taken into mines.

I know about 20 and there will probably be others.

So, definitely more than 20...