To prevent inept bills becoming law.
This web site gives many examples of citizens alienated from the state, and ecconomic loss caused by the unintended consequences of laws; dumping responsibility onto companies and individuals with out compensation; and increased bureaucracy reducing the freedoms of British culture – particularly as we harmonise with the EU. Good citizens have got used to breaking the law by overlooking to fill in the right form, or in ignorance of the laws requirements. Many of our betters think that they are above the moral code, and even the law. Our education system has largely been replaced by low level training establishments. (Education requires understanding and though, whilst training only requires remembering set routines). All this has been achieved by democratically elected goverments that themselves have no certificates of competency to govern. (I appologise for being facetious).
To counter balence the Commons a strong upper house is required. One that has expertiese in all aspects of life. This cannot be achieved by party politics. A collegiate system will not be perfect, but it could be very much better for the country than the ill-thought out existing situation.