Old chestnut indeed!
I would agree with Clive, Chris and Gordon.
Living on a county border I spent many years being a member of two teams before the National was formed. Whilst mutual aid existed, it gave me the full benefits of both organisations and a much better chance of being called out. It never caused any conflict or confusion.
Whilst that no longer applies, I can see the merits in certain situations.
I currently volunteer with several other organisations that benefit from 4x4R support and co-ordinate that on their behalf without any conflicts regarding membership or insurance.
It is just a matter of only wearing one hat at a time.
The bottom line is we are using our vehicles for the benefit of the community and how individuals reach that goal is a personal choice.

I live in hinckley which is in leicestershire and is on the edge of the a5 north side. On the oposit side of A5 is warwickshire and just over the boarder from hinckley is nuneaton. I work for west mids ambulance service in coventry. When had my discovery 1 when an ambulance got stuck they relied on the duty officers bmw x5 to pull it out but sometimes the tow rope had gone missing meaning they would call for recovery that would take hours. Once i went out to take my tow rope to the duty officer him expecting me to turn up in a response car but i had gone in my d1, x5 got stuck so i towed it out then i towed ambulance out. I was not normaly alowed to do this due to insurance purposes aparently. They could of called wm4x4 response out to do it. If i was a member of wm4x4 as well then insurance sorted as i would be there as 4x4r not wmas staff. Also when i finish work i could do couple of hours during the snow periods helping out wm4x4r. Cant do recovery stuff now as got a skoda octavia scout 4x4 like most nhs response cars but still have my kerr in car for use with duty officer.

Basicly if i was some sort of member to wm4x4 as well as lr4x4 as my parent group i surely would be more use. It takes me 20min traveling through cov n warwick area an 5-10 min in leicestershire area to get home.