In reply to climberuk:
We drove from Calgary to Vancouver a few years ago when visiting our daughter in Central BC. Unfortunately it was the year of the floods, so we didn't get to Banff or Lake Louise, however we did plenty of other sightseeing. The Icefields Parkway is a must, as is the ride up on to the Glacier - if only for the experience of being in one of the monster Glacier buses. The Athabasca Falls are worth a visit on the way north to Jasper, as is a visit to Maligne Lake - complete with boat trip. The Glacier trip and Maligne Lake trips are not cheap, however we did not think them a rip off. From Jasper, head west to the Mt Robson visitor centre. The walk to Kinney Lake below Mt Robson is worthwhile -- especially in June when a lot of the flowers are in full bloom. Do not underestimate the distances or driving times - especially as speed limits are lower than in the UK - and the cops have highly efficient on board radar in their cars! Expect to see a lot of trees and little in the way of wildlife apart from Deer (and bighorn sheep). In 6 weeks and 2000 miles driving we saw 3 bears and one Moose. ( One of the bears was just along the road from my Daughter's house!)
From the foot of Mt Robson to Kamloops, there's not a huge amount of interest, whether take the northern route via Prince George or the Southern Route via Kamloops. Both will bring you to Cache Creek, where you can either take the Sea to Sky highway via Whistler and Squamish, or down the Thompson and Frazer Valleys via Hope towards Vancouver. Sea to Sky is the most scenic route, and there are a number of good side trips. Joffre Lakes are highly recommended. If you follow the Frazer Canyon route, make sure to stop at Hells Gate and take the Airtram.
The next time we go, we will probably go via Banff and take Highway 1 through the Rockies to Golden and the Okanagan before heading north via Kamloops to our daughter's in the Cariboo.