There's no "fine". If VM miss a scheduled appointment, they pay you £25. If you book an appointment and you aren't available you get charged £25. Seems very fair to me, since otherwise the full cost of missed appointments falls on all customers.
The higher amounts referred to in the press articles are for other companies, worst of whom are the rob-dogs of Vodafone, who in addition to having customer service even worse than VM's low standard have the audacity to steal £110 for a missed appointment. That's simple thievery, because the actual cost of lost technician time on a single visit is about £20-30 including all overheads and typical travel costs. Anybody joining Vodafone broadband needs their head examining.