Replacing rubber radiator hoses with silicon hoses- waste
Flushing out and replacing with new coolant (any suggestions on good products?) - any old coolant is fine
Straightening fins on intercooler + a good wash. - pointless, bending fins might crack stuff, leave it.
Cooling Panel - huh?
Aftermarket Thermostat - waste
Aftermarket Radiator cap - once again, waste.
As people have said, it runs @ 80 because that's exactly - how it was designed.
Running a 70 degree thermo will potentially keep the car in cold start, take forever to warm up etc.
Once it IS as 80 - a 70 degree thermo won't make any difference at all.
The radiator does the cooling, not the thermostat.
Increasing the pressure via a higher pressure cap, simply means there is more overall pressure in the system.
If temps are @ 100 degrees you WANT it to blow, as once again that is how its designed as the system will over pressurise and could damage all sorts of areas.
Also the typical ebay piping kits/replacements/silicon fail as they are shit. I've busted I think 3 Samco hoses recently, and on Autobhan88. I will never change from stock (or similar quality/non silicon hosing from places like Enzed/Pirtek etc) again.
If you want tips to keep the car cool in summer - there are two.
1. Flush the radiator and fluid.
2. Don't drive the balls off it on a 40 degree day.
Pretty simple and more effective than most of your suggestions.