I was worried my car would not fit between the bollards (I own an SUV) and as there were no signs preventing driving through the access opening just ahead of the bollards I drove through the access opening.
Except there were !
The bollard facing you as you drove towards the road restriction has an arrow on it pointing down and to the left. This is the sign, and it is mandatory, not advisory.
These restrictions are there to prevent large vehicles, mostly HGVs from using the road, ot her than emergency vehicles that are permitted to use the central lane.. If your vehicle is too large to fit the narrow lanes clearly you have to either buy a smaller vehicle, or not use that road. However whilst you say it's 1.85m wide, this is normally the width between the mirrors on each side, not the body.
I assume from your narrative that you have received 2 PCNs for the one contravention. Can you please post up the 2nd one. This should not have been served if it is for the journey that took you through the restriction. It is a basic principle of law that you cannot be penalised more than once for a single transgression.
Also looking via GSV, there seems to be no advance warning of this restriction at all, and if one comes to it with a wide vehicle, has no means of turning round and going back.