I've had three ADSL Max lines running via a MLPPP bonded Linux router PC (using the now defunct bonded router CD) for several years via Enta Net. I'm around 1.2Km from the exchange and my sync speeds have always been max at 8Mbps.
I was recently automatically migrated to the 21CN which caused a load of problems. I think that basically the Sangoma ADSL modem cards in the router weren't compatible or needed new drivers/settings etc. Anyway, to cut a long story short, I removed that and switched over to a Netgear DSGN3700 ADSL2+ router. After a lot more faffing around I'm finally starting to see decent sync rates (after a DLM reset - not sure what this is technically called? - as the old profile was messed up by the old router). I also have Annex M on one of the lines as a test.
So my question - I'd like to keep two of the best performing lines with Annex M and bond these using MLPPP (mainly to achieve the best possible upload speeds as I upload large files regularly for my business).
Has anyone got experience with bonding (not load balancing) ADSL2+ lines with Enta or anyone else in the UK (affordable!).
I've been searching around for routers that support this and have seen a couple but not sure if they'll do what I need. I'd also like a reasonably good firewall with (hopefully) features as flexible as the Linux IPTABLES i've been used to on the old bonded router. I also have a block of external IP addresses I'd like to route through to my network again.
Any help most appreciated

Paul.