Just to update this;
My stb has been doing the 'flashing light' thing (explained in my first post) for the last 4 nights..... always seems to be between 8 and 9pm! Each time i phone up NTL to report it but by the time i get through all the options the light comes on solid. Typical.
The last bloke i spoke to said he could do nothing as the box was currently working ok. Does anyone here know what the signal levels on the box should be?
Any other ideas or should i just phone NTL now and demand a new STB?
Please help! :o