In general terms, are there any providers that offer the type of upstream requirements on non-cable / non-fibre line?
Quite simply; no.
The only non-cable (I assume you mean cable TV) and non-fibre services available are all based on ADSL1, ADSL2 or ADSL2+ products.
If you were to switch your broadband to Sky LLU, you'd be able to get the fastest upload available from your exchange (around 800kbps - i.e. what you have already).
ADSL2+ AnnexM can go faster (but AFAIK only BEthere.co.uk, and ISPs they wholesale to, offer that). It comes at the expense of a little download speed and only works over very short lines.
In any case; this is irrelevant as BE don't operate out of your exchange.
Bonding is the only option and as your upload speed is limited to around 0.8Mbps (due to the small amount of providers operating out of your exchange) you'd need to bond at least five lines.
You are correct; if you want to bond 5 lines, you'll have to pay for five line installs (at between £70 to £130 a line - depending on who you go with), you'd then have to pay five ADSL connection charges, five sets of monthly voice-line rental (because ADSL is not available in this country without a working voice-line), and five sets of ADSL monthly charges.
You'd then need bonding equipment etc.
There are ISPs which specialise in bonded lines (AAISP is one) but it's going to cost you big-time.
The only other option is a leased fibre line, and you're talking thousands of pounds install, and serious money for monthly rental.
It might be simpler telling your son to find someone down the road (in Hastings) to host the video streaming service.
Hastings exchange has BE LLU (so anyone close enough to the exchange can get up to around 2.5Mbps upload speed (with BE Pro), BE did offer a bonding service (so two 'AnnexM' lines would give 5Mbps total upload (but they appear to have put applications on hold for now).
Additionally; Hastings is due to get FTTC 40Mbps down (10Mbps up) fibre next year.
Have you thought about moving home
EDIT: just in case you do move to Hastings and BE suddenly open up applications for line bonding, they price line bonding of two 'AnnexM' lines (giving a max download of 44Mbps and a max upload of 5Mbps) at £65/month, with a connection charge of £85 (which includes the bonding router).
You still need two working phone lines (£130 line install - ish, plus around £10 to £13 a month line rental for each line).
ADSL2+ with BE
DL Sync around 4.8Mbps
UL Sync 1088kbps
DG834GT with DGTeam firmware
Edited by adebov (Sat 20-Aug-11 17:53:05)