Thorn Housewarmer S Backboiler

I want to fit a new thermocouple to a very old Thorn backboiler.I have removed the fire and stripped down the boiler so that I can see the thermocouple.At this point,I thought it would just be a simple matter of pushing it out of the bracket next to the pilot light(a spring clip was holding it in place),but.when I pressed it down,there wasn't enough clearance underneath to get it out.It hits the bottom of the boiler casing.I have removed the connection to the flame failure device with no problems.

Any advice would be welcome as access to the pilot jet,thermocouple,etc. is very restricted.

Thanks

youm in dangerous territory fella