Hi Kaz33
Thank you for your question which I can gladly answer. I am a former HR manager of a law firm.
Standard operating hours of law firms in the UK are 9.30am until 5.30pm (Monday to Friday with 1 hour unpaid intended as a lunch break) - a 35 hour working week.
By law if you work more than 6 hours in a row a company has a legal obligation to provide a 20 minute break (which is usually unpaid) no later than the point at which you have worked 6 hours.
Most include this in a 1 hour lunch break or for simplicity round the 20 minutes to 30 minutes for lunch as frankly 20 minutes is not enough time to properly eat and rest in a full days work.
You have requested flexible working and wish to work 9am until 4pm (which is 30 hours of work, with 5 hours intended as lunch breaks).
Your firm have not been very creative or communicated with you. You should have had a conversation around the request and had everything clarified before a new contract was issued to you.
You don't actually need a new contract you could have had an addendum to your existing contract, because in say 1 year you are eligible to make another flexible working request or you may even wish to return to your original contract. A new contract comes with additional risks, does it document your continuous employment date? Also a contract should clearly state that lunchbreaks are unpaid purely as clarification.
As the firm operate standard hours from 9.30 (and therefore the practice manager/first aider might not be at work at this time it's more of a risk to consider allowing these as a regular pattern of working) I would have suggested:
Start 9.30 (rather than 9am) and take a 30 minute lunch (to take into account the 20 minute legal break requirement) and leave at 4pm as you wished.
Or better in both parties favour, work 9am until 4pm with 30 minute lunch, with this option you work 32.5 hours and only miss out on 2.5 hours of productivity and salary.
However dependant on a risk assessment being conducted and considerations being made your suggestion 9am until 4pm (taking the hour each day for lunch) would also work well.
I think you need to consider more the benefits of taking the hour long lunch break - 30 minutes isn't really long enough to take a break away from your desk, eat, go for a walk, exercise etc. An hour break will rejuvenate and refresh you and set you up for the afternoon and the evening with your family.
If you wish for me to loook over your employment contract and advise do reply back.