Flat Battery & Jump Starter Question

[AlJ]

So, last Friday, I tried to start my 2020 Mk4 Yaris Dynamic and the screen went bonkers. All sorts of errors, including key not detected. It then told me to depress brake and then push 'start' as usual, then the brake pedal just pushed back! The car obviously wasn't going anywhere and wouldn't even lock the doors, let alone fold in the door mirrors. It did lock the hatch, though. It just wouldn't open it again.
Anyway, Toyota Roadside Assistance sent a very helpful chap in his AA van who soon got me jump started. He advised I kept the car on, in 'Ready' mode for the next two hours. I dutifully did this and the car has behaved itself since. 
I've looked through a number of similar posts on here and noted it's a fairly common problem. I'll admit to basically having abandoned the car outside the house for the last couple of weeks, so won't be doing that again. 
I've also decided to invest in a Noco GB40 jump starter pack, just in case. I've even already familiarised myself with the positive terminal within the fuse box for the red lead. Obviously, the black lead won't stretch to Toyota's recommended Earth point on the opposite side of the engine, so two questions... 

1. Is the Noco purchase a good idea?
2. Which point do other owners of this and similar packs use to attach the black lead? I've heard the studs on the suspension mount would be suitable and I think read it somewhere on here. 

[Jasper.]

Hi AIJ,  

I had exactly the same issue with my 21 Yaris Excel and was given a Noco GB 40 that I used to jump start mine. I used one of the nuts on top of the suspension for the earth lead and it instantly fired into life.

[Jasper.]

Yes I think it's a good idea and wouldn't be without mine now.

 

[AlJ]

2 minutes ago, Jasper. said:

Hi AIJ,  

I had exactly the same issue with my 21 Yaris Excel and was given a Noco GB 40 that I used to jump start mine. I used one of the nuts on top of the suspension for the earth lead and it instantly fired into life.

 

Just now, Jasper. said:

Yes I think it's a good idea and wouldn't be without mine now.

 

Many thanks, Jasper, for your replies. It always helps to hear from somebody who has actually done it. Much appreciated. I'll put in my order on Amazon.