Macbook repairs from unauthorised service providers?

I have a macbook pro which was purchased in late 2012, and which I have had no problems with up until this point. However, a couple of weeks ago when I opened up the macbook to turn it on, there was a folder with a question mark flashing on the screen. Results obtained from googling this problem suggested that the macbook could not find its system software, so I tried internet recovery using command+R on the keyboard. Initially this looked promising but when prompted to select my wifi network I realised that the macbook was not picking up my wifi network (I tried entering the name and password manually but had no luck with this either; I was simply left with the spinning 'loading' icon).

I used the online chat to speak to an apple 'genius' who had me try this same process once more; same result. The genius then recommended I take the macbook into a apple/stormfront store to have it looked at. I did this, and spoke to two members of staff, the first of whom explained that the macbook would likely have to be sent away from the store to have the problem diagnosed, at a cost of 50 pounds to myself. However, he said that as the macbook is currently just under 5 years old, this 50 pounds and any repair costs may be covered under UK consumer laws, which was nice to hear! He set me up with an appointment in store a few days later to have it looked at properly.

I therefore returned a couple days later to the same store for my appointment, which was with a different member of staff. After I explained the problem yet again, this person again told me about the process of sending the laptop away. BUT he also recommended another local computer store that I visit first to see if they could open the macbook up and perform a quick diagnosis or fix of the macbook (the idea being this would save me sending it away/waiting for it to be returned, etc). Although unsure about this, I would have visited the store on that day anyway, had it not been closed for a bank holiday.

Since then, I have not made any more efforts to return to either the storefront store or the other shop that was recommended to me. My laptop will still not turn on at all, and so I cannot use it at all. My question, then, essentially boils down to this: should I try visiting this other store again to see what they can do? Or should I stay away as they are not an authorised apple retailer etc? Plus, even if they couldn't fix the problem, would any work they do on my laptop invalidate the protection I currently have under UK consumer laws? OR should I simply return to storefront and have the macbook sent away to be looked at properly by them?

Any advice would be appreciated, I can provide more details on the macbook if necessary. Cheers.