I think if the subframe was broken you wouldn't even be able to sit on it. Its just the plastic underneath the top seat unit fairing. They are really flimsy at the back end from memory. You can see where its broken in this picture.....as said it'll be easier and less stressful to fix yourself. Problem is its probably soured your relationship with the dealer which in turn can put you off the bike !
I wonder if someone has pushed down on the rear to see how firm the rear suspension is, like you would with the front Maybe the the mechanic at the showroom
If the motorcycle is not of satisfactory quality then you are entitled to a remedy. if you make a trader aware that you want the motorcycle to be 'fit for a particular purpose', even if it is something that it is not usually supplied for, then you have the right to expect it is fit for that purpose. The burden of proof will be on the consumer. They must prove that the goods are faulty within the initial 30 day period in order to reject the goods. After the expiry of 30 days the burden to proof shifts to the Trader. The Trader will be required to prove that there is no fault with the vehicle. Looks like you can reject it within the 30 day cooling off period as being unsafe to ride in present condition. Depends on how much of a bargain it was compared to the repair costs that would influence you decision.
dealers hate it but you do have 30 days to reject a vehicle for any reason Even “you don’t like it” Take it back if you don’t want it and get a full refund I brought mine off them and it was not until about a year later I noticed a big scuff under the clutch covers They are useless