Hi Patrick and a warm welcome to the forum
It is sad that your new employers have cut the overtime you have been accustomed to earning, but I think most businesses are feeling the pinch at the moment, and overtime is usually the first thing to go.
My first reaction to your post is that your expenditure looks very low at £620 for someone with a mortgage. Have you included all of your expenditure in this figure - including housekeeping, clothing, running your car, all household expenditure and standing orders. As well as the known outgoings, you will also need to make a provision for contingencies. An IP will be able to take you through all of this, and advise you on the sort of allowances you ought to make to ensure that your future repayments are affordable, and you be allowed to maintain a reasonable standard of living. Do you live on your own, or is anyone else contributing to the household as well?
The creditors that you detail are largely amenable to IVA propsals, albeit the Student Loans company are not. Given the level of their claim, they could be easily outvoted were you to propose an IVA to creditors, but you could also consider a DMP as well which would see your creditors eventually repaid in full - but over possibly a longer period than the 5 years of an IVA.
You will need to address the equity in your property during the final year of an IVA, by seeking new lending at a maximum 85% loan to value, and using any surplus raised to pay into the IVA for the benefit of creditors (subject to affordability). A DMP would avoid the need to do this, but of course it could take you longer to pay off.
I would recommend a direct chat with an insolvency professional to explore these, and other, options further.
Regards, Melanie Giles, Insolvency Practitioner