If its a sewer then Thames Water do it for free - had ours replaced in Feb 2020 by them - check their website .Manhole covers on private property are their responsibility
Still looking for someone to do this job. Looks like my responsibility according to Thames Water website. I am no expert but guessing a general builder could do this? Any leads gratefully received.
As part of having our front garden done Kieran O’Brien (Landscape Initiatives) replaced a manhole cover for us. Highly recommend him: 07713 488730