They will now have to keep London and its visitors secure with less money than they areused to.
请问老师 they are used to 是后面省略了什么吗？
原句有误。they 跟句首的主语 they 是一回事，不是 money，所以用 are used 为错误。改为：
They will now have to keep London and its visitors secure with less money than they used to.
【翻译】他们目前不能不花比以前要少的钱，来保护伦敦及其游客的安全。
含义是：目前财政紧张，资金短缺。（可能是新冠肺炎疫情是什么原因吧）
比较从句是无需补全的，假如单纯从理解角度，可以如此：
They will now have to keep London and its visitors secure with less money than they used to keep London and its visitors secure with.
【注意】比较对应项（much）及其被修饰的名词（money），在比较从句中决不可以出现。即：much money。
比较项不可以在主从句出现两次！“参与比较的名词” 假如在主、从句中作主语，会是如何呢？比如：
More people hope to live in the countryside than used to.
More people hope to live in the countryside than did before.
More people hope to live in the countryside than before.
以上3句都正确。但在从句中，不可以重复用 people 或用代词 they 作主语。不可以说：
More people hope to live in the countryside than they used to.
More people hope to live in the countryside than they did before.
总之，一句话：“比较项及其被修饰的名词”，不可以同时出目前主、从句中。
