Ok - I got onto the builders merchant that supplied the cylinder yesterday and they have contacted Megaflow on my behalf.
They state that "the Honeywell V4073 is the correct valve and was the one supplied with the cylinder and meets all the required regulations"
Now I am really confused!
The one supplied with the Megaflo (2 port) is not the one in your picture (3 port). The one supplied (again 2 port) should have been installed in addition to the one in your picture (again 3 port supplied by your installer).
Be in no doubt as to the accuracy of the information that has been contributed in replies on here. No offence intended, but it appears that everyone you've contracted have f***ed up. The quickest way to p*ss everyone off here will be to attempt to put any credibility to what you've had done.