I work in the industry (disclaimer!)
A lot of speed issues are cause by ropey internal wiring. BT sell (giveaway sometimes if you ask nicely) a new front plate for the master socket that solves the problem. The other thing you can do, if you have cordless phones, is disconnect any extensions. Some people report that just disconnecting the ring wire (orange/white) solves the problem.
There's really not that much aluminium left. The GPO used it for a few years in the 70's when copper prices went berserk but it doesn't last well and much has been replaced. It becomes brittle over time and breaks. As retrobikers know, it doesn't much like being bent.
A problem in the UK is that broadband is, relatively, quite cheap. Lots of other countries have faster broadband, very few have cheaper or more widely available broadband. It means that there's not much profit to be made and it's hard to justify investment.
If putting someone on one of the fibre options costs somewhere around £1000, it takes a long time at £15 a month to make a return - and bear in mind that prices continue to fall and future regulation might mean that you have to sell that £1000 connection to a competitor for only a tiny amount more than it cost. That tends to mean that Virgin and BT only roll out new kit where they know they'll have a shot at making a return - and that means places where lots of people already buy broadband.
Telcos aren't rolling in cash these days. Virgin is heavily indebted, BT has tens of thousands of pesky pensioners living longer than was expected to make payments to. So they have to borrow money to build stuff, but not many banks will be impressed if you ask to borrow £1000 and tell them it'll take maybe a decade to pay them back. Assuming you want to make some profit yourself for your efforts, I think it's hard to make the numbers stack up.