Redundancy final pay wrong

Hi there,

So bit of background, i worked at my company for 7 years - however 2 were on a contract so "officially" 5 years, in December they offered company wide voluntary exit ptogram, i enquired but not applied and was offered £14k to leave, due to personal reasons i.e fiance from America was going to move to the UK instead of me moving there ....so i turned it down based on their promises of no compulsory redundancies in the future and the future training provided that would be on offer...i was told they were making redundancies the following March (of course) and i was selected as part of that process and my new package was the standard which turned out to be £5,700 in total (including Holiday etc)

Everything fell apart in those 3 months where i turned down the money, my relationship ended and i was about to be made homeless after a series of arguments with the step mother, the final straw was losing my job or at least being put into a consultation period for 45 days which would of ended the 9th May, the start of my consultation was the 28th March...i worked as much as i could before this all got too much for me, trying to cope with all 3 things and saw my Doctor who previously told me about my past depression being a risk for work and i was off for a couple of weeks a couple of years ago... he signed me for off citing work related stress / depression on the 23rd April, 13 days before my consultation period end and 7 working days in May.

So i got paid my normal wages for the month on the 20th May as they stated what would happen, £1,765 and they said they would deduct the redundancy amount from that which id get paid the following month i.e today however my total i just got paid was £3,867... they have not paid me for my sickness leave which ive already looked up and says i am entitled to 28 weeks of sick leave in the contract handbook, it looks like i am owed around £617 am i correct in this?

What can i do?