You reckon I could win again this case?
 

Well, come back to my car tonight and found that I got a bloody fine slapped on my windscreen.

I parked on a single yellow line after 6pm, which here is free to park on without a pay and display ticket.

Opened up the ticket and read that I was parked on a taxi rank. So I looked around, from what I remembering seeing, there isn't any thing written on the floor that said it was a taxi rank.

There were signs that displayed "Mon-Sat 8am-6pm Pay at Machine" then above it it says in a much smaller sign "No loading 6pm-8am except taxis" The second sign above it is considerably smaller, and at night it's harder to read, especially the "except taxis" being written underneath everything else.

I've been on their website and found this:

"There is no obligation on the City Council to allow any time for motorists to obtain change for Pay & Display machines. The motorist should arrive equipped with change for the machines if he / she intends to park in these spaces. In practice our Parking Attendants carry out observation for 5 minutes before issuing a Penalty Charge Notice. However, once the Notice has been issued, it will not be cancelled in circumstances where the motorist has gone to obtain change and this has taken longer than the observation period."

Now I looked on my ticket and it says "Observed from: 21:28 to 21:29". That's 1 minute.

You reckon I could challenge the case or should I just cough up and pay the damn £35 that's not going to put to use except the DoT's pocket.

How much would it cost to go to court?

You can try, but it's certainly not a trump card.
In practice our Parking Attendants carry out observation for 5 minutes before issuing a Penalty Charge Notice
They put the "In practice" there.

I'd challenge it especially if the parking sign is above head height and not at all obvious at night.

Taxi ranks usually have yellow wording on the road and even a plain box, if there was none of that I would definitely challenge it.

That's the thing. It wasn't even a yellow box there. It was just a single yellow line, a bit thicker than the standard one but either way, there was no yellow box surrounding it. Just the white box for normal cars.

I'm gonna go back where I parked tomorrow just to make sure. If it's everything I originally thought, I'm gonna challenge it. If it isn't, and it's my fault. I'll cough up the damn £35.

make sure to take pictures so that if you do go and challenge it you have proof to what your trying to explain

good luck