Ive got a 2012 subaru xv 2.0d 147bhp, uk model. Runs great, but my son turned my key clockwise while engine was running. Now my car struggles to start 

Id say it needs a new starter but they are very expensive. My dad who is an electrical enginner thinks we might be able to repair it as possibly just the gear thats broke. 

Can anybody help me with buying a starter motor repair kit suitable for my car. Or any advice or experience on what damage is usually done when ingnition is turned when car running. 

It looks like the starter for your motor is used on other subarus, might be possible to get a cheaper used item from a breaker?

Have a look through this site for ideas on cross model parts - Although US orientated it should give you some options against buying a brand new item

ttps://www.1stsubaruparts.com/v-2014-subaru-xv-crosstrek--premium--2-0l-h4-gas