There is no reduction in the RRP, but everywhere else I have checked is sold out and stopped taking pre-orders a long time ago, e.g. Amazon, Game, Play.com, Shopto, Zavvi, HMV etc.
I pre-ordered my Wii from Argos when everywhere else was sold out and had it was delivered perfectly on time.
You've been able to pre-order Wii Fit from Argos for a while now, but the delivery dates you could choose were always before the release date, which made me wary of ordering it. (When you get to select delivery it only gives you times during the next 10 days as options).
But now you can select dates from 25th April onwards (and can order Saturday 26th April delivery for another £2.95 - handy for those with no-one home on Friday) on top.