I think you have removed both panels together as the front panel is only thin and it clips in so you have more then likely removed both at the same time on this.
If you have access to the evaporator unit which is the cooling fins you see at the bottom of this in the right hand side is a vent hole.
Feel in there as ice can block up in that vent and this stops the air blowing up the vent to the fridge.
As its completey defrosted now its going to be hard to feel the cold air circulating as its defrosted now.
So make sure that vent is free from ice and then refit the panels and see how it goes from there.
If the fridge still isn't cold but the freezer is then all it can be is the control board at the top as we know the damper is working as in test mode it opens and closes so it only leaves the control board at the top at fault.
Now the bad news is you cannot replace yourself unless you have the programming kit as the boards are sold blank. They have to be programmed up with the software for them to work.
Now if you wanted it fixing the cheaper option is to get Hotpoint themselves in as they do a fixed price repair for £110 so for that they will replace board and program it with there laptop. Were as if you were to do yourself you would need to buy the part then the programming hardware key and then the smart card which will take the price for all that over £250 so not even worth it.
But check the above and see what you find with the ice in the vents and let me know.