I think you’ll need the pad because I’m not sure you’ll find (or even lift) a 3600mm lintel :-)
you can avoid the thermal bridge by trimming off 20mm garage floor and putting in rigid insulation (or even expanding foam). Personally I’d do rigid insulation as it’ll stop mortar etc filling in...
I'm building an extension in the SE and my BCO actually suggested I dig pads and build off 1800mm lintels rather than dig the usual footings. This might be because I'm building alongside a 1800mm Victorian wall which has seen better days but lintels will be just below ground level in my...
