West Sussex Motors Worthing - shocking service issues! HELP?

Help on how to get a fair solution from this dealer would be appreciated! 

Potted history, 

1. -- Car purchased 31.1.14.  
2. --Car new at registration 1.9.13.  
3. --Ex showroom model, 29 miles on clock when took delivery.  
4. --Model - Skoda Roomster 1.6tdi (105 bhp) SE
5. --Purchase price £13,995. 30,000 mile service pack inc. in deal.
6. --Fault with vehicle first brought to dealership’s attention August 2014, after 7 months of ownership, car aged 11 months

Parts repaired and replaced on 5 visits to repair shop over 5 months - initially presented itself as a coolant loss problem. First 3 visits - pressure tested and no faults diagnosed - 4th visit =

1. water pump repalced
2. coolant sensor replaced
3. 5th visit - EGR valve replaced
4. Last week have identified suspected cracked head gasket and/or split cylinder head(s).

Catalogue of problems over the 5 months and now major engine fault -they refuse to provide a replacement car even though it apparently falls under the Skoda UK Rejection Policy.  I can't be sure though as they won't send it to me.. Apparently they do not have 'a duty of care' to send it as it's an internal policy. 

Finance have offered to buy back this (now) 16 month old car and pay me the princely sum of £1,230 to walk away. (I have paid c. £7,500 off the car and the'll buy it back from me for £7,500, leaving me £1,230 equity).

And yes, I've tried Skoda UK csutomer care (Tom Chadwick - supposed Executive customer care is dealing with it), VW Finance under Credit Consumer Act and Dealership.

Being bounced around royally between dealership and Skoda UK, conflicting policies, advice, shocking treatment and service for a clear engine failure warranty issue.  Please send any advice...the sales team at West Sussex Motors are just refusing to budge.  Want to sell me a new car on a new finance deal - don't see why I should when I have such a catastrophic catalogue of quality  and service issues!!

Thanks in advance all!