8v suddenly won't start !!!!

[gasketface]

Hi all.I'm on a real downer as iv'e booked my car in for MOT tomorrow afternoon after having to cancel once before due to missus issues !.

Been working on car for past 3 days and today was my last job,fitting the cat back on after running a decat.

All went well,had to put the front on blocks so i could get a jack under (coilovers) and started o.k. to do this.

Iv'e had car 10 months,no issues at all,starts on the button.

After refitting cat,car won't start.Everything goes dim,so thought battery might be low.Charged it in situ for 2 hours,no joy.Charged another one,still no joy.

Iv'e got 12v at battery but my voltmeter in car shows 8v roughly.

P*ss*ng down with rain now and time is short.

Have no hair left to pull out !!!.

Have checked and double checked wiring but i'm stumped now.

Any ideas ?.

Thanks,

[Screech16v]

Try jumping it off another car with a healthy battery,will it bump start?

[GOLF-MK3-GTI]

Ignition Coil

[Len]

Have you refitted the Lambda?