Faulty Laptopthat crashed before 1 year warranty

Bought a Lenovo laptop end September 2014 which was replaced within a weeks time because laptop would not boot and from what I understood the mother board had crashed. This was than replaced with another laptop same model and 10 months later I have the same problem my laptop did not starting up at an event that I was hosting with presentations for 200 guest. I took my laptop in to supplier Micomp on the 3rd of August 2015. I was told that its gone into Lenovo for repairs and a part had been ordered which would take a month to arrive from abroad and than three days later I received a call saying it was ready. Repairs were done in the warranty period and since then it has gone in every week because it has not been working properly. I run a business that is dependant on me being professional and proactive daily with my sales team and for the last three months this has set me back completely and has had huge implications on my business. This week again my laptop is flashing strange lines across the screen and I cannot shut down and when I do it takes ages to reboot. The supplier I bought the laptop says he cannot unfortunately do anything more for me and its Lenovo responsibility