Five Picture Stories: Excelsior Days

I had a very rewarding tutorial with John on Tuesday; the work that i started on my first ' Person at Work' project has developed into a project that i would like to continue in the UK.
As John said there are some good pictures,but i need to start approaching the customers for portraits, dialog etc to gain a more intimate insight and produce a stronger project.
Even though the owners gave me permission intialy, they have been hestitaint about photographing their customers, one of the long term waiters 'Kosta' is very interested in my project.
John said i should approach them with some pictures of my work and put the idea of making a project on them (the owners) and the cafe. I need more access and less secret type images.
I wanted to ask the other teachers and students about the ethics involving paying for subjects in these projects?
Any advice feedback appreciated.............
I know many photographers do; Pieter Hugo,Ed Kashi (even though he expressed a dislike for this approach)
the problem is, how to approach the subjects in a paid manner, an advert in the window or through the owners?
as many of the customers are people with drug and alcohol addiction problems as well as sufferers of mental and addiction related illnesses.....where will the money go?...what image, idea willl that project to them about photographers,students etc?......plus many of these people have been tolerated,if not liked by the owners over the years and it is one of the few places on the Cowley Rd that will even let them in....so the advantage of being paid by me, may lead to trouble with the owners?.....but i know many of these customers struggle to buy a coffee, so maybe i can buy them a meal or a coffee...but without patronising them?......a dilema.
I have taken portraits of homeless in the past, but only a few particpated, but they didnt want money,they belived i was genuine and trusted me...even though this often left me feeling guilty when i walked home to my comfortable flat in Cardiff,while they smoked crack and slept under the railway bridge!
This project alowys me to be much more removed than that.....
AGAIN AND ADVICE AND FEEDBACK ON THE WORK AND ADVICE ON HOW TO PURSUE THE WORK AND INFORMATION AND ADVICE ON THE ETHICS OF PAYMENT FOR SUBJECTS PLEASE

The Excelsior Cafe

Andeas and Georges Koumy
emigrated from Cyprus to the UK in 1954.
They opened the 'Excelsior' in 1961.
It hasnt changed much since the 60's but now its dark confines seem to attract clientale who live on the fringes of modern society.
I wanted to record the ambience of the cafe, its age and the characters that sought a brief shelter within its melancholy confines.