fungi matters

Evening all, looking for some mushroom advice. I sowed some lemon balm seed in a mixture of old an new compost, covered with plastic and hey presto...I have some lemon balm seedlings but also several little mushrooms! What is the best thing to do? and can anyone suggest reasons for their growth? I'm guessing warm, moist places and the fact that I had some old compost in there? Should I pull them up, chop at soil level or will they be ok to leave? I'm not sure if they use up nutrients in the soil like plants do and therefore steal from the little seedlings!
Thanks in advance

Everywhere being the operative word..............all over the place by seed
So if you don't want to be invaded make sure you chop off every bit of flowers or seed heads............be afraid be very afraid

My lemon balm grew for a couple of years then simply died off.
I don't have any now.

I would not worry too much about them unless they are going to grow large and shade out your seedlings.
Most funghi are saprophytes which means that get their nutrients from dead and decaying material.
Many plants such as the Vanilla Orchid cannot survive without their fungal partner and it is now thought that as many of 90% of all plants, trees etc have some form of symbiotic relationship with funghi where the funghi supplies water and nutrients to the plant and the plant provides sugars manufactured through photosynthesis to the funghi.
So be nice to the little fellows unless you find Honey Fungus then apply Napalm.

Regards,
  Argaric