Manhole cover

[the2ems]

Hi, not sure if I am in the right part of the forum, but I couldn't find a section on outside drainage. I want to buy a new manhole cover, but the dimensions shown on the ones at Wickes are smaller than the one I have. The house where I need the cover is probably from around the 50's so the cover is a solid cast iron jobby. Have the sizes change since going metric, and can you still get the older ones?

Cheers