Thanx Phillip, great explanation.
Actually my next door neigbour had same problem except that his phone line was very noisy for both voice and speech. After 6-8 months they changed for him the subscriber card at the exchange and his phone line was crystal clear.
So I guess its not the wires that are bad, its the exchange itself. My guess would be that there might have been bad varistors on my phone line subscriber card that were generating the noise, plugging the phone lines in the mains must have fried them and line back to normal again.
As you said, who knows!
The important thing is that I can access the internet from home at last, haven't been able to that for ages, Sod the phone company and their sucking service.
Regards
Mahmood