I always use Bosch plugs, but to be honest NGK or Bosch do the job.
Carb cleaner, all do the same job.
I would clean the dizzy cap, check its not cracked/carbon rod is okay.
Check the air filter also, often overlooked, should be clean.
Good idea to run Fuel System Cleaner through it, Forte is good but difficult to get hold of, try some Red Line S-1 or S-2 (super stuff) which can be got from opieoils.com. Or other uk suppliers just type brand in google.