how can i fix my robinson and willey storage heater ?

i cant find model number. It is aprox h 705 w 1005 d 170 It is possibly 3.4kw and combi.
I believe it may have been used to dry clothing on.
I have taken the front and side pannels out, but can not locate the re-set button. On right hand side there is a circular plasict piece with wires attached and a sticker with numbers: 501875, T-O-D 60T11, S0521, L145-40C.
The unit is connected with two wires independantly to the wall. There is power comming through.
Any advise please. Thank you