Thanks for your reply kva.kva. I got the definitive answer from Check Point in the end.
We needed 1 x Enterprise License, which includes Smart Center Management and an unlimited license for 1 Gateway, plus 3 x VPN Gateway unlimited licenses.
We were 'pleased' with this as there is a huge difference in price between 4 x Enterprise Licenses and the above.
I found the link below pretty useful for definitions of the licenses (requires a User Center login)
https://usercenter.checkpoint.com/uc...yLicensing.pdf