Thanks very much for the reminder, Inte.
It's time I actually purchased one of these, even though I currently have no working track at home.
Got to plan for the future.
This unit is available in both 25 and 40 amp variants and, as far as I can see, is the best value Power Supply Unit readily available in UK. (The US guys get much better deals)
For those interested, here is the Rapid Electronics PSUs
link, which gets you a largish PDF document and the particular unit is, about three screens up from the bottom of the document.
Later Edit: IF that link no longer works, (revamp of Rapid Electronics' web site) then please try THIS ONE
Order codes are
for the 25 amp model
for the 40 amp model
Voltage is variable over 3-15 volts, with an additional fixed mode of 13.5 volts - a sensible standard figure for slot racing, but with the facility to vary if you prefer.