When it comes to External Wall Insulation systems there are very strict procedures in place to ensure the homeowner is protected against poor workmanship and poor materials. The Building Regs and the Inspector from Building Control will ensure the system being fitted has been independantly tested and accredited as fit for purpose and that the contractor is qualified to install the system .
Any builder or contractor that fails to mention Building Regs or to steer you away from them should be avoided at all costs. Similarly we would always recommend you check which system the builder is recommending and that he is accredited to fit that system.
Most importantly of course make sure you get a good quality materials and workmanship guarantee