Help me help friend!

ifeelstupid

Hi
Posting for a friend who is not a Boardsie.
Apologies in advance for the long post.
My friend has been working in the same place (hospitality industry) on and off for 9 years (went p/t for college and took a year out for travel).
Was getting on well, clean work record, no warnings etc. Boss has always been a bit of a bully but my friend is very laid back and secure in their abilities so was able to let this over their head.
Friend has never been given a contract or pension options. No structured finish time/overtime – leave when the work is done.
There was an incident last week that left my friend with no option but to give notice. Because they have no contract and are paid weekly notice period is one week. Boss was to take annual leave so friend gave notice at the weekend with intention to leave at the end of the month so they would stay to cover leave. Very reasonable in the circumstances I thought. Boss obviously thought otherwise!!
Boss arrives at 5pm yesterday and tells my friend to finish whatever they were at, leave now and they will post their P45 to them.
Initially they were prepared to let this go but after sleeping on it my friend is angry at this treatment today. Basically they have asked my advice on what to do. Obviously I’m on my friends side and only advice I have is to put any further communication in writing. I’m guessing notice should work both ways but I have no idea
1, what their entitlement to notice/pay in lieu is and
2. if they should pursue this and
3. how to word it?
Hoping my fellow (and much more knowledgeable) Boardsies can help
Thanks

ifeelstupid

Mods, please lock up this thread - I have started another one. Thanks