Boardman road bike bottom bracket
It should not require greasing after only 5 weeks, unless it was not done originally.

A noise of that type can be caused by basically 4 things in the Bottom Bracket:


Loose or worn bearings - in this case unlikely because of the age of the BB
Loose or dry BB cups 
Loose crank bolts or crank arms
Dry chain - not likely, given the stated fix by your shop.


Options 2 or 3 are likely given the fix described. Both would be repaired by removing, greasing and retorquing the BB.

The most likely cause after such a short time is that they were left loose or dry during assembly, and that the shop or mechanic was talking CYA. 

But that is difficult to determine from several thousand miles away. You can be confident that the maintenance does not need to be performed every few weeks. Your twice yearly tune up should be enough.