Thanks for the input so far, in reply to the questions:
I'd assume Tiscali was a no-no, I'll check with the beancounter early this week, I'm on a weekend maintenance shift right now (5am Sunday morning)
yes, it's an average of 120GB per month incoming to most places.
There's a lot of design stuff flowing in and lots of video scenes (one lot does video enhancement, another does product design) The end-products are usually couriered or posted out.
The town offices are unrelated (in business arm terms) to the heavy users but do have 20-30 users 9-5 Mon-Sat doing your average "stuff". No voip though. Ntop keeps an eye on abuses quite nicely for us there.
For reference, the "old product" is/was F2S "unlimited" ADSLmax Premium 8M down / 800k up for about 19+VAT per month, all non LLU. We haven't had a single "heavy use" type letter/email in 5 years of continuous running under F2S.
At the start of the month it's was rebranded TalkTalkBusiness - then suddenly throughput at all sites seems hard-capped at half a meg down, the domain email has simply stopped, the user pages are innacessible, customer support is 9-5 Mon-Fri only. We spent all day Thursday and Friday on hold.
Thankfully we don't have any business-critical domain-based email with them but it's a huge shock compared to 5 years of quiet bliss. It feels like we've had our throats cut.
The reason for the comparatively huge traffic per site is largely down to the fact that F2S used to be quite a cool ISP a few years ago, apparently large hunks of traffic like that is OK for domestic endpoints (we're talking about before Tiscali/Pipex/Opal got their sweaty mitts on F2S - before my time but around 2004 was the start of the homeworker programme I think).
When the DSLmax products came out (and the workfromhomers became more organised) the remaining lines were migrated into F2S. Bear in mind the traffic is heavily policed by our office, work owns the CPE and PC kit and if the worker wants non-work internet they must buy their DSL down their personal PSTN line - our lines are paid for by work and are off-limits for the snivelling pirating porn-grabbing kids
A&A would be the Dream Team as they speak our natural lingo but the cost is huge; another worry is an incoming DDoS or SIPflood eats units (we've had a few nasty surprises on the A&A failover links this last year - paying for unwanted incoming SIP packets to be dropped at the CPE gets expensive)
Actually, I wasn't aware we were in negotiation territory, everything has been off-the-peg F2S until now (decision by my previous boss) but have been (very!) cheap and no trouble at all, until they changed to TalkTalkBusiness. I even had one of my own home lines on F2S, only one real problem (email server restored (to baremetal?) from backups) in 4 years.
That said, I didn't really think 120GB was a lot of traffic on a business line, most of my sysadmin mates top 200 per month at SOHO sites under their remit. I'd guess the majority of that is damn iPlayer and Youtube.
Bulk / vISP/ reselling to self is certainly viable, it's just I simply didn't realise we were into that territory yet, given we have such a disparate spread of sites over 3 vastly different business sectors. I'm hands-on not a negotiator, I just do what I'm told and they sort the money stuff
L2TP sounds fine to me and would be very little setup here as our kit is centrally managed and monitored (by me and my little gang), though we don't have any presence anywhere useful. We're all 857/877's with centrally rolled-out Linux/BSD so a lot's doable for very little config work here.
Thanks for suggestions so far, I need to talk to the bosses this week it seems. Links duly noted.