I had bought replacement line from B&Q and re-round the spool myself but the line broke continually during use. I checked that all was done correctly and conclusion was that quality of the line material was poor. This spool with line produced by the maker of the strimmer works perfectly! Worth paying the extra cost.
Very expensive for what it is, the line does not last long. Better to buy the cord and wind it yourself even better to use 2 mm. might be worth it if line was stronger ie 2 plus mm