Ludlow Thompson are now my agent of choice for lettings (I have a number of properties in SW17). They are hungry, pro-active and the admin which sometimes used to let them down has now been thoroughly improved by the current management.
The rents they achieve are always top of the market and usually delivered very soon after instruction minimising unwanted void periods. They have also proved themselves a valuable source of help in the running of the tenancy with help on everything from safety checks to sourcing new furniture at short notice.
In summary - excellent without reservation. If you have property to rent out don't do it without calling them first.