I agree, you must recieve a Key Fact Illustration when a recommendationhas been made to you. But out of interest, did you not recieve a copy of the mortgage offer well in advance of completion? This also has the information set out in exactly the same format. At least at this point you could have uncovered the issue without commiting to the mortgage and had opportunity to recover any costs to that point if alternative Northern Rock products weren't suitable. The lenders sends these directly to the customer and one to the solicitor.
Did you sign the application without reading through the form, namely the product section?
I know people rely heavily on the expert and rightly so, but to commit to such a large financial commitment without having seen anything in wrtting to what you applied for until a year later?? Not sure the complaint would hold much ground unless you can evidience the mortgage broker breached regulations.
Another reason Northern Rock were regularly used was for their generous income stretches. You may not have had much option with regard lender but more with product. This may not be applicable in you case if the stretch wasn't required. A lot of times customers main goal is securing the property and possibly this is the prioirty the advisor was working towards.
You have a right to any information held on you by The mortgage shop under Data protection laws. Have a look at the factfind and suppoting documetation in relation to your file. This will help you with any possible case.
Don't mean to be negative, but this is what you may be faced with. Better to be prepared.