I have found it hard to buy exact replacement ballast units in the past and so one has to fiddle around trying to make it fit. So likely better renewing whole lamp.
There are two basic types of lamp. Those with a induction ballast and those with a HF electronic ballast. The HF electronic ballast is in the main more expensive and far better as it ensures exactly the right amount of power is feed to the tube and the higher frequency also removes the stroboscopic effect. Normally with the electronic you get more light from same tube and the tubes last longer. Plus they use less power and can better cope with voltage variations.
Seems you have been unlucky with yours. The older induction ballast with over voltage uses more power than written on tube up to 20% more where 250 volt is feed to 230 volt fitting and where the voltage is low may fail to light completely as for example 220 volt feeding a 240 volt fitting.
So although in your case the electronic ballast seems to have failed I would still replace with another electronic type they are much better than the induction type.
PS I had a google to look for your lamp "Super Slim Circular Ceiling/Wall Light 16W 2D" and it is sold for £20 plus vat, so is it really worth messing about getting spare parts? I put "2D D151" into google search. There is also a 28W version of same lamp D130 it is 65mm bigger 360mm diameter instead of 295mm diameter but same looking unit.