shower going hot then cold

atarisrocks

had a new shower put in 6 days ago after the old one wouldn't turn on.

it a triton enrich cold feed and has been used 4-6 times. i went to use it today and the water changes from hot to cold. so it hot for maybe a min-3 mins then freezing cold for 30 seconds to 2 mins. the water flow stays the same. no other water is running at the time (taps, toilets washing machine)

i had a blown bulb 2 nights ago that turned off half the switches in the fuse box including the shower so i dont know if it is linked but i have used the shower once since the blown bulb

is there a short term fix i can do so i can shower until i can contact the landlord tomorrow