help with oil burning boiler?

we have had it up to here with this oil burning boiler we have. for 5 weeks we have iregular water and heating issues. in total we have had 4 days of hot water and heating. this is what we got

a oil burner outside, it uses a winter/summer switch 1x thermostat and 1x over temp warning light.

in house a room radiaitor control stat

in house we have a digital control unit which has a 7 day timer setting. for example

monday 5am-9am 12pm-4pm 6.30-11pm. etc etc etc

we have it set off unitll 6.30-9.00pm 7 days a week as we out at work all day so pointless. it on the winter setting so it will allowing heating to be used.


THE PROBLEM

it doesnt work lol . for example for 5 weeks the boiler will run heat up and deliver hot water and heating then over temp light will come on and whoosh that it no water no heating. like today we got home never used anything today as we at work but the over temp light all ready on ??????????? we got cold water and no heating again. we have told the landlord 100s of times they have had bata out to repair and have repalaced the the over temp stat. it worked for 3 days and then back to the old problem.

any ideas on it??