You can't run a series of spurs off one socket on the ring. You can only have one spur off each socket on the ring and not a series of them off one socket (i.e a radial). Your best bet is to break into the ring. If you have to use a joint box for this, it must be in a permanently accessible position. You only need to pick a main up from the house to do the lights. Make sure you use earth sleeving and brown tape/sleeving on any blue wires which are being used as switch wires. You can connect it yourself but you must get a PART P Certificate from a registered electrical contractor. I believe there is no set fee for a PART P inspection so ask who will charge what before you make the choice. My firm charges £40 for a small domestic installation. Hope this helps.