They were fined a total of just over £116 million as part of a leniency deal offered by the watchdog to companies that owned up quickly to anti-competitive behavior.

主体句式: 

They were fined a total of just over £116 million as part of a leniency deal…

结构分析: 

这是一个复合句，其成分比较复杂。offered by the watchdog to companies

作为一个分词短语来修饰前面的deal, 而后面that引导的定语从句又修饰companies。

句子译文:

他们总共的罚金只有差不多一亿一千六百万，这是作为监察部门对那些积极坦白反竞争行为公司的一种宽大处理的一个部分。