Never underestimate how low someone will go to protect their arse.
Shit all over you, lie, manipulate, falsely accuse you of what they in fact did.
I have seen and heard it all.
Those with the most detail notes, records, date stamped documentation are the ones that came out of it fully intact.
Your detailed notes of everything, especially the harassment during the holidays, the lies, the screaming intimidation, and finally your realisation that fraud has been committed to cover their actions, whilst trying to cover their tracts and blame you are crucial.
Document every bit of it, date stamped.
In a similar situation my friend came out smelling of roses.
Her detailed notes which were the basis of all her statements, which were unbelievable to read, left the top management in stunned disbelief.
She went the Grievance route, which is most effective, as all her allegations, facts and proof can end up at the Employment Tribunal if a satisfactory resolution isn't found between both parties.
They found a resolution, that she was very happy with, because there was no way they wanted her highly inflammatory case of a publicly quoted company, seeing the light of day.
She is still working there, on her terms, unbothered by the middle management that thought they could fxxk her over.
They know that she retains the right to raise another Grievance if anyone looks sideways at her again, and she will.
Contact ACAS asap so you have advice today.
Screen shot all messages and your phone log which indicates the timeline.
This is a dose, but with a cool head you can emerge from this.
Once you have copies of everything, and your arse covered, consider going out sick under direction of your GP.