These days with the Internet right there at everyone's fingertips, if someone properly knows how to use it and check their facts with reliable sources the internet can help you save a lot of time and money. Especially when it comes to advice, the people who know it best are the ones who own the product not the ones trying to promote it.
I'm not certain why someone would think that you can get information that is just as helpful as a dealer when more than likely a forum with responsible participants might tell you what the problem could be but then they're still going to advise you to call the dealer. Forum's are great because they give you a chance to hash things over, but they don't replace the actual point of service.
Of course NOT, because always dealing with any car's own service department will give more satisfaction than dealing with its forum. Why? Because a main dealer gives exactly the right product from the manufacturer of that car when a car needs to be repaired. In this case if seeking advice from a Jaguar service department you will get more standard advice than the forum.
Calling a Jaguar dealer would be a better way to seek advice about the repair of a Jaguar. Many times people on forums have really great advice, but sometimes they do not. You have to be able to weed out the good advice from the bad advice. Also, you have to wait for answers when posting a question in a forum, whereas if you call a dealer, you are likely to get an answer right away.
People on forums do not have the same credential or sense of responsibility as somebody who works at the service department at Jaguar. Getting advice on a forum would be a big mistake especially on a matter that is dealing with the mechanics of a car. It is the best option to contact the service department at Jaguar.