Thats not what direct line says in the schedule or the small print? You need to watch what these halfwit call centre people say.
I was with direct line and they never asked me about 'cost option accesories' (what you are saying in reality). Neither online nor on the phone.
They just asked make & model and value and whether it was 'modified' or not. There's no way leather seats is a 'modification' IMO.
Try event-tyres web-tyre-chooser
http://www.event-tyres.co.uk/ to see whats in your size - it appears only bridgestone i'm afraid.