So, you'd rather screw bits of Airbus airliners together that are made by other people rather than design and manufacture the really complex and sexy bits, like the wings, engines, fuel systems and the like. BAE were offered the S320 assembly line many years ago but turned it down as there was very little added value in merely assembling the things.
If you don't believe me about the SBAC quote, try this from their successor organisation;
The UK aerospace sector is a successful, vibrant, high value high technology engineering, manufacturing and service industry that generates good returns to all its stakeholders. With over £20 billion per annum in value added revenue and employing over 100,000 directly, and over 220,000 indirectly, the industry is one of the UK’s largest exporters adding around £2.8 billion annually to the UK balance of trade and involves around 2600 companies across all regions of the UK.