The job was pretty painless all together, it took a couple of hours all in.
The OR guy turned up promptly, plied him with tea n biscuits, discussed all the options i wanted and he was open to them all. We both decided on option 2. So he relocated the master to the extension in the end with the new i-plate, pinned the data cable on some skirting boards and through a couple of walls to a new data socket in my PC room, so both the modem n router are located there. We both decided going external wasn't a good idea due to limited access down one side of the house, which i knew might be an issue.
Before all that he also tried plugging the OR modem straight into my existing ADSL extension which sync'd at 29/9 on his test socket kit, which as i suspected would be pretty bad as the extension is using cheap phone cable.
So end results are; I'm sync'd at 53/11. The initial ookla speedtest results are 43/11 which is a bit below what i expected (falls in between the BT impacted scale) but its good enough for me seeing as I've been stuck on 4.5MB ADSL forever.
Hopefully that will increase a bit in the "10 day" learning period. I'm approximately 4-500m from the cabinet, this is just a rough guess as i have no idea how the cabling is routed to my house, it could well be more. In which case i believe my sync speed is pretty good?
Kasg you were right, internet was immediately available as soon as we plugged the router in, i left it for 15mins as per instructed.
Thanks again to everyone on this thread for their advice and help.