Extending External BT cable

Hi

I would like to move my master box. The cable comes from the pole to the front of my house and down the wall and then goes in the rendering above my porch and then out at the bottom of the wall in the kitchen. I would like to bring the cable in through/by my landing window and site my main box there. Can you tell me what cable i need to buy to extend the outside cable, as there is not enough (as in goes in to the rendering) to bring it through/by the window. I have seen external junction boxes on web sites, and I was thinking ??? I could cut the cable just before it goes into the rendering, put it into an external junction box and then extend new cable (??) into/by window on landing and site my home hub and master socket there.

1. I need to know the right cable to buy
2. If I want to put extensions from this new box, what numbers and colours I need to put the extension cables to?

thanks

No, it belongs to BT not you.

Sorry.

I know.

But the original box cannot even be moved an inch and I need my new kitchen fitted, and I don't want to be crawling under the unit every time I get a problem. Is there any way of running a new master box from this box??? then

Ask BT.

Do it yourself and have a problem they get a bit stroppy.
Making joints you cannot access isnt the done thing either.

The simple rule is that the incoming wires and the first (master) box that they connect to belong to BT and should not be touched. The outgoing wires from that box belong to you.
Moving the master box should only be done by BT.
Is the master an old style box or a newer NT5 (google for pics if you don't know)
BT might be amenable to replacing an old box.

If the box would be accessible for future BT maintenance (even if not very convenient) after your renovations, could you leave it where it is and run your internal wiring from it to a more convenient point at which you could install your own NT5 equivalent?

Just pay for it to be moved,by the time you have purchased the cable and joints and the time spent doing it,you would'nt save much money anyway and as has been said you should not be moving the cable that you rent off B.T