Aye, considering you're paying £2000+ either way, I'd say it's worth going that extra 500 for 'actual' insurance that won't be pulled out from you like a showman's tablecloth.
As @RedGiant said in your other thread, it's definitely worth contacting some insurers directly.. Admiral, Bell, Diamond ect all have some policies you can see on comparison site... and some you don't and you need to ask (Those 3 are also basically the same company). Some places like Direct Line don't quote on comparison sites at all. When getting a quote on the phone with them ect, there's no harm in simply saying 'It's more than I'd hoped, can you do any better and save me shopping around?' worst they can say is no and it might be in the agents interest to go that extra mile for you.
When considering mileage it can make a lot of difference. It's obviously a crime to lie to an insurer, but they only ask you for a mileage estimate after all...