I have been receiving invites from various groups which is ok, but they are now becoming a bit too regular,  I was wondering if this can actually be stopped without actually blocking the sender.  Thanks.

Bah Humbug!

They must think you would be an asset to their group. Accept the flattery.

tell them too stop inviting you or just accept them all. Some people just randomly find you and invite you.

It is tough being so popular...