Just to follow up,
We are booked to go out next week so a while back went to Quidco and used the broker carhire3000 to get the 7% cashback. Prices were reasonable after shopping around but higher than when we were out in May which we put down to August holidays.
This week we got our carhire voucher through, would you believe it but carhire3000 have placed my booking with goldcar! Can't believe I am going to get fuel spanked!
Decided to consider cancelling and book elsewhere and noticed prices have now dropped by quite a lot. Carhire3000 have now changed my booking and downgraded from a fusion to a 4 door clio for £167 including 0 excess. £100 saved will cover the full cost of the spanking and the kiddie car seat. Result.
So in future maybe consider using carhire3000 and then check prices just before you go and rearrange. Not sure if many other car hirer would let you do this.