There is a few systems to look at.
If your looking for an installed system then i would suggest looking at 'Smart Nav' it is the latest system out which has satellite navigation, traffic updates and speed trap detection in one unit, its made by traffic master in co-operation with RAC. This unit is updated constantly with the latest traffic info, so if there is a crash on the route you have choosen it will route you round it.
£
799 inc. VAT next day DEL and
installation
If on the other hand you want an easy to use portable system, i would definately say go for something like the 'Magellan RM700' it is a very good unit with its own 11gig hardrive which has all the mapping infomation you could dream of so you wont need to keep plugging it into a pc, its a cigarette lighter powered unit, with a suction pad to the window (OR and additional Dash Mount).
£
799 inc. VAT next day DEL
(Prices were taken from
www.nav-now.co.uk 0871 7500 111)
Hope that helps