[UK] Hourly rate query
I am leaving my full-time salaried job in the next few months, with a plan to explore other avenues of work. I have saved for this anticipated time out of employment, however for security and schedule I do plan to pick up some part-time hospitality work etc.
My current job revolves around monthly processes, and although I gave my one month notice in June, for business continuity, my employer asked me to stay on longer, which I have agreed to on a part-time basis.
They have assigned a new person to the role, who I have been training. Although as the work revolves around monthly processes, picking this up is taking them a significant amount of time (as there is only one opportunity to review the tasks per month).
Although my personal circumstances mean I intend to leave permanent employment, I have offered to provide flexible, contracted training support for approximately 2 days per month in order to provide business continuity. My employer are currently finalising the checks regarding IR35 and internal procurement policy, but this looks like it will go ahead.
I plan to invoice monthly for my services, but I'm not sure what is appropriate as an hourly rate. My current role is salaried, with holiday and sick pay benefits, but works out to £25 per hour. Would £50 per hour be too much?
I know I should increase the rate to account for self-employment and the specialised training role I'm going to be providing, but any suggestions on an appropriate amount would be appreciated.