Hey Si,
Bit of where i'm coming form on my advice..
I quit my job when I realised my heart wasn't in it (and it was nicely paid) mainly when they wouldn't train me further than I got too, so I decided to quit it and go and do a degree, in something I was interested in, whilst I was young enough not to have much tie downs. After passing it I got offered a Phd which (obviously) I took, and I've never looked back!
Theres a lot of may's and maybe's on the first option, have a good look in to it, if your going to start a course i'm sure that they are gonna start in sept (assuming that yours was due to start in March??), which gives you lots of time to look into other courses, on this note if your "based" in an area and cant move you might be a bit stuck for the places that you can study.
On 2, I would try to go for what you want to do, the way I looked at it was "its better to regret something you've done that something you aint", end of the day it's only money following what you want to do, and your gonna be happy (hopefully) doing somethinng you want rarther than something you dont, and hey if it all goes skywards you've still got it to fall back on anyway so wheres the loss!
As for 3, One of these might be more benificial than doing a masters, not too sure but to me it might be like a CISCO course for networking, hence on the back of that and a good portfolio you can get in at a higher level than a degree/Masters graduate?? Not too sure on this just my thinking might be worth a the stamps, time and emails???
4 - If you go with your option 2 then i'm sure youll be doing this anyway??
Hope this makes sense.
Cheers
"No pressure, no diamonds" Thomas Carlyle