thanks for your advice ray, but this is with one of the big clubs, and gone down the legal path, the van  is over the first 3 years, so we pay half the cost, the last van we had was a land ranger 660abs from avondale, a much better built caravan,
		
		
	 
I  do  wonder if there is some lack of clarity about  where the liability  might  lie, which  could change the way  your problems might  be addressed.
The rights, obligations  and liabilities are quite different  under the manufacturer's warranty compared to your statutory rights which are with the seller not the manufacturer.
Let there be no doubt, the Consumer Rights Act (2015) has real teeth which  stay  sharp regardless of any action or repairs undertaken through  the manufacturer's warranty. That is why every  manufacturers warranty has to  include a phrase like "This warranty does not diminish your statutory rights"
I'm  guessing  it's the  manufacturer that  given you the pay 50% ultimatum.  That  is  quite legal  for them,  becasue of teh way the Manufacturers warranty is  written, they write it and you  can take it  or leave it. but  the CRA sets out  quite clearly  the seller is responsible if they sell  faulty goods or goods that  are not  durable or fit  for purpose. 
On the assumption the fault has not  been caused by misuse or damage,  there is a real possibility the  fault was present  at the point you  took  delivery,  and that  means the seller sold faulty goods. That is contrary  to the CRA and providing you  can provide evidence from  an accepted expert assessor, you  have a strong  case to  bring a claim  against the seller (not the manufacturer)
Claims of this type do not  need the manufacture to  agree as they  are not  legally  part  of the contract  of sale.
Each case should be resolved on its own facts,  and if you  have actually been able to  have unimpeded use of the  product despite the fault  being  present, then the seller can counter claim  for the use you  have had.
Ultimately  the CRA is designed to put the consumer back into the same place they would have been if the fault had not arisen -  which is a fair way to look at it. 
The fact the manufacturer has agreed there is a warranty liability  is a strong  point  that  might  yield better results with a CRA claim.