General cylinder head

[jac20]

My engine needs a new cylinder head. at a main dealer cost of £3500 i am wondering if Volvo are partly responsible for the bill. my xc90 has done 122k and had a full volve service at 120k (end of July 2013). as i picked up the car i noticed for the first time a warning light saying that the coolant level was low and that i should stop the engine. i did this and the service manager and mechanic came over to see what the problem was. they opened the resevoir cap and topped the coolant level up and sent me on my way.
however the problem persisted in the following weeks and i took it back to the dealer as i was not happy with it.
it transpires that the cylunder head is warped. the engine has never overheated and the temperature guage has always read 'normal'. i am told that this is very rare!, so rare that they have had to order a replacement head cylinder directly from sweeden. apparantly it can not be skimmed - volvo says this.
i agreed to the replacement, it's the family car and i have to get it fixed. when i dropped off the courtesy car this morning (27/08/13) i informed them that i wanted to keep the old cylinder head. i neede it to examine to see how it became warped and whether there was any financial recourse against volvo. i was told that they could not do this as it was going back to volvo as this was the deal £1k off the cost of the new head or something like that. i was also told that volvo would skim the head and sell it on.
i said no as this is my property and i needed it. this was the first mention of this. it was never discussed when i agreed to the new cylinder head.
anyways i am livid to say the lease.
i would be grateful to receive any advice on my options going forward.