Bosch leads sets are good quality, as are the Champion branded ones.
Unbranded are questionable.
Magnecor are good if you are on gas I have heard, but I have no practical experience. £72 plus VAT for the non-racing type of lead set.
On your sparks issue, I'd change the plug leads AND the distributor cap, and buy a branded product again, don't go for anything without a name on the box, or anything not boxed come to that. There's a huge amount of 3rd-world produced kit out there that motor factors just love the BIG margins on, but it is poor quality material.
Lucas or Bosch, stick to those brands and you won't go far wrong. Land Rover will sell you the original fit equipment, which is probably Lucas in your case.
Peter