I just got an email about this. If anyone is renting a car this month in the UK, you might be interested in a 20% off sale they are offering for rentals during the month of April. Caveat: you must book AND collect the car during April, so you can't book it and then try to collect it in May or June.
I realize most travelers to the UK have probably booked their cars already, but it's certainly worth taking a look at, as you can always cancel your first reservation and make a new one.