Sari, if it counts for anything I have got ALL my line sets from The Kite Shoppe and they are top class. Theresa has been very acommodating and helpful to me even though I am in another country, so I'm sure she will sort you out.
Incidentally, my 120 set for the clinic is on it's way to me right now - figured I should get a little time out at 120 before I get to the clinic to make my life a bit easier.
I see you're in BC - I'm sure there is someone there who can let you have time on their 120's before the clinic and then Theresa can sell you a set of your own at the clinic itself. My outdoor flying is on 20, 30, 50 and 80' sets (indoors is normally 12') and I haven't found the lines to be any kind of limitation in learning a skill - it just alters how big your wind window is.