I would recommend Bushells, they sold my flat after three attempts with other agents.
Rachel was very good, keeping both parties (buyer and seller) up to date status of the sale with us all.
I also found Liz to be very helpful and honest regarding what the flat should be valued at, rather than overpricing and it staying on the market for ages. She priced it realistically and it sold within weeks.
Bushells are the one to use on Lordship Lane :)