15 flashes doesn't tally with any of the known faults. Applying logic, by 15 minutes into the programme, the machine should have filled, started tumbling and probably be into the heat sequence.
So, filling. You can probably hear water coming into the machine - is it running out at the same time? This can because by the drain hose being set too low, or fed to the bottom of the standpipe, leading to syphoning. Assuming fill, is the drum tumbling? The machine will try a few times before putting up an abort (clunking round).
Heat is where it gets complicated. There is a heater, a thermistor sensor and the computer board itself. Any one of these can and does fail; so if you have any doubts as to your own abilities check the Directories section for a UKW engineer in your area or put your postcode up in here and someone will pick up on it.
Whatever you choose to do - PULL THE PLUG FIRST!
Which bit of "Unplug it" is causing the problem?
Stop eMailing me. This is a perfectly good forum - use it!