sneaky saleman

I have bought my suite but it won't be delivered for another few months. My complaint is about their salesman. He was extremely nice, offered my friend and I a wee cuppa and we had a great wee banter for 30 minutes or so and then down to business. I wanted a 2 seater amd a 3 seater. I decided I wanted the better quality of leather which added an immediate £200 on to the sale. He then proceeded to tell me I could take the interest free. I asked him to work it out and he told me a monthly amount to which I agreed to. It was now time to sign the paperwork. I noticed he had added insurance cover at the price of £179. I was absolutely livid as we hadn't discussed it at all. He literally just added it into the monthly payment. I told him to get it off immediately and he said he would have to do the paperwork again. He came back 5 mins later with another saleman and told me this was standard procedure to witness me signing the deal. As I went to sign it I noticed he had added £25.99 for a cleaning kit. Again I told him to get it off. I honestly wish now I had just cancelled there and then. They should be procecuted for this sort of thing. Not everyone would have picked up on their dishonest tactics until it was too late.