Woeful service from Std Trust

My father passed away in November 2016 and my mother passed away in February 2017. They had a joint Will with Standard Trust so everything was left to my mom initially, and then she had a new Will drawn up at Standard Trust leaving everything to me and my two siblings. At the time that a Std Trust consultant first reviewed my dad's documents we were told it was a 'small' estate that would be wrapped up within three or four months. Everything was moving relatively smoothly with the consultant keeping in contact with us. She then resigned around mid 2019. I can't even be sure about the date because they didn't have the decency to advise us and introduce us to the new consultant. Since the new consultant took over the estate, things have deteriorated to the extent that I actually don't even know who to deal with anymore. She is attempting to get money paid over from two institutions in the UK so that the estate can be wrapped up. Whilst I am aware that companies in the UK do not like to deal with email or pay funds over by EFT, the service from this consultant has been nothing short of atrocious. Initially cheques were posted from the UK to Std Trust, but because of the poor postal system in South Africa, the cheques were stale when they arrived. So Std Trust requested fresh cheques. Needless to say, when they arrived, they were stale. Std Trust was quite prepared to continue banging their collective heads against the proverbial brick wall by requesting fresh cheques each time until I asked them to get the cheques couriered. They then decided to get their solicitors in the UK involved, at a cost to the estate, and since then the whole scenario just goes round and round, and round .... The consultant at Std Trust can never say anymore than she is waiting for the solicitors to respond, she will get back to me when she has an answer etc etc etc. Meaningless drivel that can simply be copied and pasted. Furthermore if I don't prompt the consultant for a response, there is never anything forthcoming. so I generally start my email with "it has been a further two weeks since". Despite having included the CEO of Std Trust on several occasions, the only promise I get from her is that she will refer the matter to other Std Trust staff in order to resolve the situation. I now have run out of ideas. Who do you complain to, if not the CEO of an institution?