Hi coolsnakeman and welcome.
>> i have aliminium cabling from the exchange to the cabinet and copper wire from there to my premises.
I'm afraid this is bad news for you and theres quite a lot of lines in the UK that still have some sort of aluminium on the line which adds extra resistance and a higher attenuation reading. Sometimes you may be lucky and their may be a spair copper pair or one that is slightly better.. but if the aluminium run is before the cab then youre often a bit out of luck :/
>> really convince them it is service effecting to my phone line
Usually this is due to moisture ingression on the joint which often occurs when aluminium is on the line.
In the UK theres nothing to actually set the standards as to what speed you should get for the line length and the only guidelines are those laid out in irrc
SINET - SIN 351. As long as the line is able to meet those standards for voice then its considered acceptable.
Its been a long hard struggle for many to get anything above 500kbps and to aim for 2Mb (as walter will verify).
Its true that the cost of replacing would be very high and this is the reason they dont/wont. I havent ever heard of anyone getting it replaced without forming some sort of campaign. There was an area near here that had TPON and it took about 4 years and campaigning by several hundred people on the estate that were affected before BT installed a copper overlay. I was told the cost once of this and iirc it was something like £80,000 for only a short run.
>> My exchange is due to go FTTC in quarter 1 of 2010
I know this isnt much help to you but... If you have an FTTC date then at least that is something and far more than lots of other aluminium lines do and there is a glimmer of hope for the future.
Sorry that I cant give you any more positive news