My brother and I were named as executors of my late mother's will.
It was a straightforward estate and involved the selling of a small property, some savings and the distribution of a small number of bequests for which a deed of variation was required in order to fulfil our mother's written and verbal wishes that the money she was bequeathing, in her will, to each of her grandchildren should be tripled. This change to the will was approved by the two main beneficiaries (myself and my brother), did not legally require a solicitor's involvement and a template document which we both signed was sufficient to increase the amount distributed between the grandchildren.
I completed the probate forms and probate was obtained within three weeks. It wasn't difficult but it was a little time consuming.
In contrast, when my mother-in-law died the following year, she had named a solicitor and her daughter as executors.
The daughter let the solicitors undertake probate and they charged the estate £5000 for their services. There was no property to be sold as the house was being left entirely to my husband's sister; there was no residual estate left to be distributed (so my husband became what is known as a "disappointed beneficiary" and he received nothing at all) and the solicitors took a full year to wind up a very straightforward estate. This was in 2016 and they were charging over £200 an hour for the work they did. They did not even bother informing my husband when they had wound up the estate but he had been told earlier that he would be receiving nothing. They eventually sent him a copy of the estate accounts.
As a previous poster has said, the executors can choose to use a solicitor of their own choice for all or some of the work involved if they feel they cannot manage it themselves and this is chargeable to the estate.
For an uncomplicated, low value estate, I would not recommend making a bank or a solicitor the executors - they are likely to take a full year or more to settle the estate and will charge heavily for uncomplicated admin work.