They should try and negotiate this with the employer.
eg Tell the employer, they would prefer to be made redundant now, rather than work the extra month. Try and get references sorted as well.
Just walking out won't do you any favours with respect to references, etc.
Also, make sure all your holiday entitlements are used up before the end of the month. (If you get paid for extra holiday entitlements, that will get taxed so you're better off taking the holidays. Tell the employer that this is non-negotiable on your part).