I'm thinking I could use marble contact paper to recover the benchtops and then paint the tile spashback a bright white

I think painting benchtops plain black with correct paint would probably work better than contact. You can get a granite resurfacing done on laminate benchtops but that way be more than you're wanting to spend. I think relaxing handles will be an effective cheap fix.

If you want Scandi or rustic then an oak benchtop on your existing kitchen and new door handles will do wonders. I know you don't want wastage but your kitchen is already 30yrs old so it's hardly that. It's the colour of the benchtop that dates the kitchen the most.

A solid oak benchtop is a very minor update that will last at least a few decades to come. If you update the splashback then use a composite board or pressed tin over the existing tiles it's economical and fast with impressive results. I'd go pressed tin in brick or traditional geometric if I wanted rustic. You can have it powder coated any colour you like before installing and they do look great in modern homes. Easy to clean as well.

Here's a smart modern example of a final look....Oak and pressed tin on white kitchen

I would see painting either tile or laminate as a last choice. Unless you have it done professionally (they use an acrylic resin not paint btw) and spray it on with professional spray guns, it generally looks terrible and wears even worse. Having it done professionally is surprisingly expensive and you may find the upgrades above are the same or similar cost.

I wouldn't change your top cabinets for open shelves unless you love cleaning and the look of clutter. It looks fab on Pinterest but that's because they've got those shelves styled with rows of uniform bowls, glasses and canisters. I have in them in my current home the only way they look good is if you do exactly the same. I bought sets of canisters and changed all my glasware for that reason. With the usual mishmash of items in a normal house they aren't a good idea.

Thank you both! Yes, that pressed tin is amazing. Oh yes, I love it!

I've researched the cost of having kitchen cabinets painted professionally and yes WOW, so expensive.

We just changed the cooktop so would have to get an electrician in to disconnect and reconnect with a new benchtop.

Thank you both