I am sure most of the photography shops will do a good passport photo. I used the one opposite Seckin's in the street across from the PTT in town. Tell them it is for a passport and they know what size to do them; the image is of your face is enlarged (fills the frame) in the photo so a bit different to a normal passport style photo.
Check the measurements of the photos with those on the notes and trim if necessary.
However insist that the background is grey. Although the accompanying passports notes say cream or grey, cream can be perceived as white so if you get a jobsworth you will just have your applications returned.
Also make sure that your hair is completely away from your eyes which must be fully exposed, not hidden by a fringe.
A friend of a friend had her passport returned three times because the photos weren't right.
No need for a countersignature if you look broadly the same.
I have read recently about someone who had a bit of a nightmare receiving theirs in Turkey. The Passport Office use DHL who don't have an office in Fethiye so they will be picked up by Aras cargo in Istanbul for the onward journey to Fethiye. The story I read entailed the passports not being delivered and returned to DHL in Istanbul. It was by all accounts a very frustrating and infuriating experience.
That's not to say that will happen to you though as other people have reported not to have had a problem.
Do you have a home address in the UK that they could be returned to and then some one could bring them out to you?
I chose to go back to the UK to do mine and I am very glad that I did.
Good luck
