My car has minor damage from another car overtaking parked cars on the wrong side of the road. His damage was minor, but my wing mirror was damaged and cost £405 to fix. I made it clear (at the accident and by text later) they were on my side of the road and were negligent and not driving with due care and attention on my side of the road. The car behind me witnessed it.

The road had lane markings and he could not overtake without being on my side of the centre lane markings. They asked for a quote so as to avoid using insurance if it was cheap enough to repair and avoid their excess. I provided a quote but they then offered (twice) to buy second hand parts and pay for all the garage labour. I refused.

They then offered a cash settlement which I agreed to. All conversations were by text message and have been kept. They never came with the cash settlement on the agreed time and date. I then informed the police and my insurance company. His insurance company now state 50 50 blame. How do I proceed?