If the thermostat is removable you can drop in a safety/main
thermostat such as a Sunvic (just get the right length).

If the timer has failed, Sangamo do a 1-gang 16A version with push-
button 30min-1hr-2hr boost on the front often cheap on Ebay UK
(although it only has 7hr or some such low figure battery backup).
Better than the cheapies anyway re relay quality - I've found the
electromechanical type do not like "juttering powercuts" for some
reason.

If the element has gone, check with an Insulation Resistance meter not
just plain resistance.
If it is hovering around 1.5-2.1Megohms the element is on its way out.
Best way of removing is a proper box spanner and tighten/loosen,
combined with a fine screwdriver to "chop out" the gasket all the way
around which once partly gone will permit removal of the element. Fit
a isolation valves whilst in there - but not before any vent pipe for
obvious reasons (element running, vent pipe closed off, things can get
the wrong kind of "exciting").