I'm not a surveyor but a Civil Engineer. I can confirm what the others said that it isn't a problem. The yjing to remember is that the utility company has acess rights to the manhole cover, so good advice is to ensure that you never build over it or remove it, or they can smash their way into it. I have experience of working for the Environment Agency and some clever **** built over the chamber, and entering with EA warrented officers and a court order we smased the **** out of his garage slab with a breaker on a mini digger, rebuiolt the camber but left him with a big hole.
So no worries, pal.