I've been looking for this everywhere since i saw it in tesco in Chelmsford a couple of weeks ago. Went in Woolworths in Lakeside today and they had loads (several full shelves). It was priced as £20 (reduced from £24.95) but scanned in the till as £15. Also used the 20% off voucher to get it for only £12! Less than half what everywhere else is charging! The 20% vouchers are also now valid until Sunday.
20% voucher can be found here:http://www.hotukdeals.com/item/277990/woolworths-friends-family-event-jus/