checking the temp rise on a boiler

hi there, how do i check the water temp rise on my boiler, and the flow and return temp on my heating

use a thermometer one of these would be ideal, but dont ask ME how much they cost

other brands of clip on thermometer are available

You really need a surface-probe on an electronic thermometer. Quite expensive. Cheapest way I know would be the multimeter with a thermocouple as sold by BES for just under £20. The "probe" in that case is just a junction between two wires, so it's not easy to get good thermal contact with the pipe Holding it against with something like foam would get it up to temp eventually. Also works under water.