engine temp sender location?

have not got my cooling system sorted ! MB thermostat with rubber washer thingy was £14 , recore was bit of a 'mare! they went thr' every catalogue they had but couldnt find an early diesel/auto one listed in any of their manuals(despite looking in 3 catalogues even cross referencing rad size/width) , only listed narrower 2 core rads!! got a 'custom' made/fit one made in 24 hrs cost £160 all in including new cap and antifreeze!! it was so crudded up the bottom half was stone cold when on their bench and the bottom 'tank' was so silted up it was just about over the oil cooler pipe and quite solid! just wanna replace the sender for now for piece of mind - where do i find it ? cheers elvis