From GSV of June 2022, the latest, the bay is quite long with more than one sign because of its length. The restriction is clearly there to prevent commuters parking there all day, as it only applies for a short time from 10.00 until 12.00. There are three railway stations within about 5 minutes walk.
I'm afraid your points about signs being missing appear weak, because there is one outside No 60 only 2 doors away.
https://maps.app.goo.gl/DrmjRMLTrtug8YdH9assuming this sign is still there.
There is another sign by No 77, and the bay ends outside No 80
Across the road is a pole with no sign.
This is irrelevant, because parking restrictions are separate on each side of a street so even if there were a sign on the pole it would not apply to where you parked.
To be frank, the bay is quite well signed, (assuming GSV of 2022 shows the current signs situation) and the onus is on you as a motorist parking there in what is a marked bay, to see to find the applicable sign, one of which is 2 doors away from your parked car.
Reading your narrative, can it be that you knew the restriction started at 10.00am, but overslept ?
The final thing to ask is, was this an Airbnb accommodation ? You were a visitor to the property on the street so I am surprised there are no arrangements for visitors to obtain a visitor permit.
Sorry if the above is not what you wanted to hear, but I cannot see an appeal to London Tribunals succeeding on the contravention and signage. Of course there may be a 'technical' argument relating to PCN content, or the council website for submitting representations. So wait a bit for the "technicians" to respond, don't cough-up straight away.