Havent read all the posts above but hope the visit to the GP was successful and you were well received. I've seen GPs a few times regarding similar symptoms and now have a fantastic doctor but have talked to others in the past who werent as receptive and useful to me at all.
One or two people have mentioned drugs above and what is or isn't good. I think whatever works for you is good cos what suits one doesn't suit another. As you may know by now you need to be patient as they can take weeks to fully kick in and it could be that over time you find you have to try one or two others before one really is for you.
With regards to employers I can highly recommend investigating the law and what is required by an employer for yourself. In my experience it's been surprising how many don't know the law on a number of matters (in at least one case I left with money in my pocket as a result though it's not always a result you want).
I can recommend the MIND website and after spending a stint in hospital courtesy of BUPA (not NHS so I wasn't as serious as that and thankful that I wasn't too) I had a load of therapy and can recommend CBT. For that I can recommend Mind Over Mood: Change How You Feel By Changing the Way You Think by Christine A Padesky and Dennis Greenberger - I think it's one of the standard texts that therapists use for it and is fairly simply written but when you're suffering concentration isn't good.
Two more books I highly recommend are:
Depressive illness-curse of the strong by Tim Cantopher - he is a shrink who works at one of The Priory hospitals (it's a chain which the name doesn't imply) and it's really well written; covers a wide range of topics very well including the various drugs available and a chapter for friends and family who can often find it hard to understand
The Depression Cure: The Six-Step Programme to Beat Depression Without Drugs by Dr Steve Ilardi. Published in 2010 I like this book for a. aiming to help you beat depression without drugs b. being about 6 simple things to do and being the length of a novel yet none of it is waffle and all backed up by good evidence.
If money is an issue or you're not sure any of these are for you try your library; I was impressed mine had the last of these just a couple of months after it came out.
Finally: take small steps, take it easy on yourself, exercise (whether it is walking for 20 mins or cycling for 5 hours), be wary of over doing it and getting low as a result so be cautious and stop short that way is safer and leads to faster recovery, eat 3 good meals a day - get food you like whatever it is so long as it fills you and preferably is healthy, be sociable - even a regular small amount - do not be a recluse, get an SAD light (I did this winter for the first time and it definitely helps).
I meant to write something short and sweet, listing the books only; anyway if you just do a thing or two from the above there will likely be a difference. Hope it helps some.