My unroadworthy triton cause of tyres

ok just an up date from the last post. Thanks to Rohans post about insurance with AAMI i started to inquire about my copper a/ts now when i went to the shop they told me they didnt have the 265/70/15 but they did have the 31/10.5/15 do i want them so i ask will that be fine? what will it effect?as long as all well no worries. i asked them on 2 occastions the answer was nothing itll throw your speedo out by a bit but you wont even notice it so i say well as long as alls good toss them on. after enquiring to the RTA i find that the tyres are unroadworthy (after driving around for a month or so with them on) because the load speed rating on the old tyres (and original for the ute) was 110s, the new coopers were 109q. so as unhappy as i was the girly rang the tyre place up, and with her not even having to give a reason as why they made the ute unroadworthy they said bring them in. so she took them in and no questions asked they put the correct tyres on with a rating of 112s. but heres the catch the bloke says to her the difference in tyres are 15 bucks so she rang me and after a heated conversation with the tyre yard, about how 15 bucks per tyre will be ample compensation for us bing stuffed around and how if we were to have a ding our insurance company would not of payed out because the car was unroadworthy. after more debate they decided to bring it down to 12 bucks/tyre cause they wont scrap the tyres then after all that the bloke who did the money exchange must of heard 12 bucks minus the 3 bucks for scrapage of the tyres instead of 12bucks cause we are not charging the scraping fee. so we ended up with a small victory in a lost war of paying 9 bucks extra per tyre. no moral to this but it certainly peveed me off that if it wasnt for this forum and a bit of curiosty on my behalf we wouldnt of know til probably and accident. touch wood. if you carnt trust people in the game (with reason) who can you trust?
and if your after an up date on how much they cost as i gave the wrong price before in the last forum they were origanaly 233 per tyre so now theyve cost 242 fitted twice and 2 balances.