So I started monitoring my line after I found this forum in December (thread here: http://forum.kitz.co.uk/index.php/topic,19024.0.html
Short story is that I had been on a Huawei cab with fastpath or maybe G.INP (sub 10ms pings to bbc) until I removed some internal wiring probably causing a few disconnections and maybe some temporary noise on the line and got interleaved (no G.INP for sure since December - 15ms pings to bbc).
To try to get my error seconds down I capped my download and upload so I was around 9db on dl and 15db on ul. This continued to see me have 100 - 150 ES per day on both ul and dl over the last three months so no change to status. Over that time I have resynced a handful of times. Yesterday there was a resync and instead of coming back at around 30mb/s dl it synced at 24mb/s which I would guess was down to whatever caused the disconnect still causing a problem (I suspect work by BT causing problems but who knows). I was trying to download a large file at the time so I thought screw it I am going to remove the caps as I could get an additional 10mb/s. So I rebooted the router (couldn't be bothered to do the 30 minute wait to prevent DLM caring) and I resynced with an expected rate, way above the 24 I was on. Since that resync I got the same 100 - 150 ES per day. Today a few minutes ago I lost internet and to my shock on checking the status I now have G.INP enabled, 9-10ms pings to bbc and the highest ul sync I have ever seen on the line, dl is slightly below average at 32 but I'll take that for now.
So I am just posting to record the event really, no idea why G.INP kicked in, whether it for some reason has been disabled on the cab until now or whether having a capped line for a period of time and suddenly uncapping it fooled DLM into trying it (seems a big coincidence if this had no impact), I don't know, theories welcome.