Dave,
The point about the 'tell-tale' sticker is well made.
On my 4/4 I replaced the original expansion tank ( off a Land Rover as I recall) with one of Peter Mulberry's alloy creations.
The immediate problem I had was to work out what was the optimum fill level. Eventually, I did it via a rough calculation based on the horizontal run between the radiator and the header tank.
I then went out for a few runs to establish some very basic empirical results. These worked so, like you, the Halfords tape then came into service without delay!
regards,
G
