Complex sentence: Since the 1970s, Weston has suffered a decline in popularity as a holiday destination, as have most British seaside resorts, due to the advent of cheap foreign holidays and the demise of the traditional "works holidays" of heavy and manufacturing industries elsewhere in UK.
Split into simpler sentences: Since the 1970s, Weston has suffered a decline in popularity as a holiday destination, similar to all British seaside resorts. This was a product of the advent of cheap foreign holidays together with the demise of the traditional "works holidays" associated with heavy and manufacturing industries elsewhere in UK.