Not OP, but I am also in same situation in FFX and here are the fees I was told:
Washington Gas- $14.85 transfer fee
FFX county water- $35 opening charge
Dominion Power- not sure yet
Trash- have to use FFX county service and they put the $345 bill on your yearly assessment.

I don't know if there is any way around it. I was also told there are no other service providers to compete with these companies so you are stuck if you don't like the service or fees.

Power, gas - have the sellers call ahead and tell the utilities what the closing date (or date you will take possession if there's a rentback) will be so they will have the date they should stop billing to the sellers and start billing you. Then you call on that date to confirm.

Unpaid water bills can be a lien on the house so that is worked out at the settlement table.

Verizon - you don't take over the sellers' account with them, you move your own if you have one.

What is the most seamless way to transfer utilities over to my name in the new house we just purchased? I heard some companies charge a reconnection fee, even if you'll be using the same services, which I would like to avoid. Do I just have the seller end date/ my start date overlap? Or do I need to do something else? I will be calling these companies, but I'm not sure I will get a straight answer, since they will make more if services are disconnected and then we have to reconnect. The sellers are happy to work with us on this.

I'm talking about:
Fairfax Water
FIOS
Washington Gas
Dominion Power

Thanks!