Update for the WLMG Mill Hill incident:
1. 10:15am arrived at Mill Hill branch and was greeted by the Service Manager.
2. Invited in her office and had a long chat about what happened and presented apologies for the very unprofessional manner I've been dealt with last week, specially with the safety recall
3. Informed that the gentleman who dealt with my case is no longer in employment with WLMG and will never be allowed to work in any WLMG branch in UK
4. The car was then taken in the body shop and the recalled part has been replaced within 5-10 minutes.
5. The car has been given an all round check, tyres, brakes, battery, oil etc
6. Invited in the office again while the car was being washed and getting ready for me
7. In order to restore my faith in WLMG they've offered to look into the possibility to upgrade my Audio/SatNav system to the Connect Premium version, awaiting further updates from them
8. 11:15am I was already on the way home.
I still fail to understand why I was treated like that in the first instance, wouldn't have costed them anything anyway, they would have claimed the part cost from Nissan anyway...
All in all, I think it's now been dealt with fairly and professionally, as it should have been done in the first instance.