I think my story illustrates partly why there is a high turnover of staff,,,
Spent two and a half years as a part time postie having lost my job in banking after 20 odd years. At the time it was a case of needed a job desperately and any job would do. The application process was, as has been said, ponderous and hit and miss but anyone with half a brain and bit of perseverance can crack it I think, unless its changed a lot..So having never done a manual job in my life in my late forties two stone overweight, off I went...December 2009...Xmas pressure...First walk (half a walk,,!) on 23rd December,,,sent out with a load of mail bags in my own car, knee deep in snow, no training, no hope and no idea what I was doing,,,!!
Six hours later, (finished at 8.30pm) I delivered my last letter.I went home,,half dead if I recall. The other new guy on the other half of the walk had long since gone back to the office and resigned on the spot with most of his letters and parcels...I thought the boss would have been pleased at my perseverance in the face of ridiculous odds,,,! WRONG...!!
Summoned to the office I was asked what the problem had been and why it had taken so long,,Well we had a frank exchange of views and I eventually got my docket knowing that at least it couldnt get any worse..!
To be fair it didnt and eventually I got to grips with it all and started to enjoy the job. I am now back in an office job. Ultimately I needed a full time job and there was never any chance of that happening. As for the stress of the job the biggest pain for me was working most saturdays having to book holidays a year in advance and needing permission of god to get any odd days off and the ridiculous attitude to sick leave (not that I had any but always worried at the prospect)
Also found myself working through niggling injuries as most posties do of course and despite the initial excellent fitness benefits I could not see myself cracking on until retirement and living with the pace, so account for your age. The pace incidentally which was increased by most posties still treating the job as task and finish,not using the right equipment, and thereby allowing managers to collapse walks and make the rounds even bigger and the posties (some) still battering it to get finished perpetuating the circle of doom.
So, as I sit in my office and its freezing outside I sometimes miss the lads, the banter, the fitness and the occasional early finish,,But your not that free if you can never untilise your free time because your too knackered and cant book a holiday. Its not that stressful in my opinion apart from the pressure to get finished brought on by your Park and loop partner in some cases,and the job itself can make you a bit brain dead,,,and yes most (but not all) of the managers are failed ex posties and would kill their grannys to get on or get you to do unpaid docket
Like all jobs it has pros and cons and I would do it again if I had to,,,but not in place of my so called stressful full time office job,,, The vision people have of posties strolling about with a couple of bundles on a warm spring day having a brew with old dears,,,not quite how it is...
£148 a month, £1776 a year for doing what exactly? Every time I have to train a newbie up on a duty I ask what the workplace coaches are supposed to do but I never get a straight answer! 
Nice little earner if you can get it. 
no sooner than I got shown what to do on the easiest walk in the office by an old timer on his delivery, I was put on the hardest walk in the Office and it was a b@stard of a delivery being part time I was supposed to finish at 11am I was actually finishing at 2pm every day, sound familiar today, of my intake of 10 I think over time 8 dropped out and yet I persevered the wages got better, the hours more manageable, got fitter but was still on that walk for nearly 2 years before I managed to get off it to a much easier delivery.