That's terrifying sunflowergal - £600 is a lot of money to claw back each month. It might be worth consulting a financial advisor to see if they can help. They should be free at first visit.
Apart from that you need to be really organised. It's amazing how little you can live well on if you plan.
Plan a full month menus each month and make shopping lists based on them - only buy what's on the list, so make sure to include treats. Then only shop once a month - it can be done, we have to because of distance.
One other thing I try to do is maximise each item. For example, if I take a chicken out of the freezer, we get at least one meal (for three adults) then something like a chicken and veg pie (feeds six) plus meat for sandwiches and stock from the bones - which goes back into the freezer for future use. I think my record was something like 24 meals from one chicken
Sort out insulation and heating so your fuel bills can be minimised - won't be instant saving but will help in the longer term. And pay utilities by direct debit if you aren't already - it's always cheaper and helps you budget every month - look at switching to a cheaper provider and see about off-peak savings like economy 10 (or whatever number we're up to now

). Then do washing etc at night.
Make your own washing powder etc - much cheaper and better IMHO. Vinegar and bicarb bought in bulk will see to all household cleaning.
Home baked treats - cakes cookies etc and homebrew, instead, or at least supplement of bought booze.
Grow what you can (longer term project obviously), but now you can grow sprouted seeds instead of buying leaves, for quick salads.
Socialise at home or friends houses - pot luck suppers and that sort of thing.
If you have any debt (other than your mortgage) start to sort it out now, for example get a 0% credit card instead of continuing with an interest-paying one, not after your income has dropped and mortgage has grown when the companies won't touch you- the CAB are fantastic to help liaise on your behalf if you need them.
And look at ways of supplementing your income by other means - bartering and car boot sales etc.
I hope everything works out OK for you honey. A sudden drop in income can be quite scary, but not necessarily desperate.

to you and the family.