Ive just insured my 182 with them and really cant recommend them enough! I think there is a chap there called Greg that has a clio so is familiar with all the mods RS Tuners etc...
They insured my RS tuner map along with my other mods suspension, wheels, induction etc at no extra cost. When i asked them why that was, they explained that unless the power output of the car is affected then they dont charge extra. Styling mods, braking, suspension are all covered like for like with no extra cost.
Phone them up and get a quote, then go to other companies and tell them what brentacre are offering... i found sky were very competitive, but brentacre just beat them.
Hope this helps!