travelling to and from work is not counted for the 45p / mile. if however you were travelling from home to work via a site meeting it would count, but if you were doing this regularly to the same site the tax man would be highly suspicious. at one place I worked they would allow a claim for the additional miles covered by the site visit, but if you read the instructions on the tax website they allow for the entire mileage to be claimed (but also warn that suspiciously finding a 'site' to visit on the way to work every day would be flagged up for investigation.
my car insurance is quite expensive as I am insured for 30,000 miles a year personal mileage and an additional 10,000 business, to be honest I can probably reduce the business mileage a fair bit and still manage any work trips needed, but when I originally took it out I needed the full 10,000 miles.
high mileage (120 miles a day getting to and from work) and business use all put up the cost, as does keeping the car parked on the road as opposed to garaged, and the area you live.