Have not dealt with rebuilding a gearbox yet, most i ever did was helping a friend change the shift tower on his MQ250 box for a Golf IV.
When i managed to trash my original LHY i traded it for a somewhat cheap refurbished LNY and mounted that in, a very lengthy plug & play process.
225 for a kit sounds cheap, not sure how British market looks but Dutch transmission prices are steep, where refurbished MQ200s go between 1000 to 1400 euros, with a trade in of the old box.
Looking back at the original box, i wish i had the time or a backup car, because then i would have been able to take the box apart and tinker with it, learn something new and hopefully fix it, if i was you and had the time or knowhow on how to rebuild it with a kit, i would do it.
And yeah, mates say what they say, one of mine was adamant about and trying to convience me that my 1.4TFSI has a timing belt..