When to let go?

I'm trying to figure out what to do with regards to my current auto-situation.

History
Little over 10months ago I bought myself a mint condition 1.8l Astra Coupé Bertone. Only 49k miles on it at the time.

Thought I'd got myself a beauty, well looked after etc, previous owner got it MOT'd the day before he passed it onto me without me even asking etc.

Have had some issues though, driver's side door lock got stuck for a while , but magically managed to correct itself after a week or so, still haven't a clue what happened.

I had issues in the past 4 months with ECU Light, Kangaroo-ing and cutting out at junctions. I've replaced the MAF and this seems to have made a difference. I've since read about cleaning the throttle body to aid this too, and that's the next step that I think I can do myself if I'm to continue on this road!

Big problems are however these

1 - ABS light, which has already had approximately £400 spent on trying to find and alleviate the situation. A nearside bearing was changed, I've had work done on the break units changing hoses for MOT etc, but still, the intermittent Light issue is causing MOT failure. I've been told that the garage that I'm dealing with are being unfair in failing it for this sensor, as the light, code etc does not appear when time between turning the key the first and second time is less than ~2hours (car on once => light on , car off, car on again => light off).

2 - Airbag Light is on. This has been on, and recorded on every MOT / Service that I have available to me (car came with FSH) since 2007. I have priced a replacement Airbag Module and ECU for £275 for the car, though am not even sure if this will resolve the situation! This is due to become an MOT fail in the coming year.

And smaller issues are ;
MOT Advisory that new discs and pads will be needed in coming months - quoted £315 (seems outrageous as OEM discs and pads on ebay for £60)
A/C needs re-gassing (£45)
Rear wind screen heater/demister not working (no idea)

At what stage am I supposed to say "enough is enough" with the car and replace it? As it stands, I'm hopeful that I should be able to get it MOT'd (at a different garage) for less than £50, and for it to be worth anything in terms of sale it will need to pass that.

tl;dr - I'm £400 deep in terms of fixes to simply get a car MOT'd, still another ~ £5/600 to go to keep it on the road longer than 1 year. Car is probably worth no more than £1,400. Road Tax is prohibitive at £375 pa.

Options
1 - MOT & Sale & Replace
2 - MOT & Invest in keeping her alive for 2 more years.
3 - Forget MOT & Burn & Replace :pac:

If 1 - what car do you recommend in it's stead. Will demand/need leather seats, comfort is more important than performance, won't be doing more than 5k miles p/a, mostly city driving.
If 2 - Any thoughts on any of the longer term issues? Are my numbers realistic for keeping the car alive, and roadworthy for another 24 months?

Sorry for the longwinded post, just tried to put as much info as possible in!
Thanks if you're still reading!