Always useful to know…
The assertion that “…it is a condition of the manufacturer’s warranty that work must be carried out by an authorised dealer” is a commonly misheld belief, and is absolutely and categorically incorrect. For a dealer or manufacturer to state that work must be carried out by an authorised dealer, or that all replacement parts must be manufacturer authorised, is in breach of basic European (and thus UK) statutory law.
I have researched this issue extensively, and my assertions are backed up by the Competition Commission, Trading Standards (Consumer Direct), and the Department for Business Enterprise and Regulatory Reform (BERR). Furthermore, I have personally challenged a manufacturer on this issue (Mercedes) and have been successful in forcing them to honour their warranty; they backed-down before I took them to court.
The relevant law is referred to as the the “European Block Exemption” (BER) and is encompassed within the Competition Act 1998. The law applies to all suppliers of cars within Europe, but as luck would have it, I found a link to a motor trade article referring to Nissan, which was the brand of car specifically mentioned in the original thread. In this case, Nissan were required to ‘back down’ over refusal to honour a warranty after the owner had a non-Nissan part fitted:
For further information:
http://www.berr.gov.uk/consumers/fact-sheets/page38070.html (Specifically Q4)
Naturally, if you choose dealership maintenance and servicing for peace of mind, then that is your prerogative, but by my calculations, the additional costs of ‘authorised’ dealerships are not good value for money, even when it comes to considering any value that such servicing may have when selling second-hand.
There is a lot of money to be saved by not using a dealership for servicing and maintenance!