Update: Called TS again, during the phone call the connection went up and down like a yo-yo as usual. Eventually, the chap decided he was going to speak to a superior and call us back.
About 20 mins later, another engineer arrived. Apparantly, this was one of the guys who dealt with the original fault and he was still investigating problems in the area. It seems that the incident on the 12th was caused by a power outage to VM equipment (Tesco Copdock area). Although power was restored later that night, it led to a configuration issue which took nearly a fortnight to resolve.
Around that time, VM engineers installed a piece of hardware which it turns out is clashing with existing hardware. This is apparantly what's been causing the cutouts and varying speeds. The conflicting hardware was being removed while our engineer was doing tests on our line and so far *touch wood* I'm getting about 10Mb pretty consistently.
Here's something funny - as my husband was answering the door to the engineer, a neighbour walked by and asked "Are you here to sort out the internet? It's been all over the place lately." So looks like our immediate neighbours have noticed the abysmal service too!
