In terms of getting good feedback here, are there any other goals/objectives you want to achieve with your money?
In the absence of any other info I imagine most advice will give you to either focusing on minimising current costs (mortgage) or maximising your future pension. If you're contributing 20% already you're maxing out your pension contributions.
Your mortgage is costing you 4.1%. By overpaying you make a risk free saving of this %.
For options 1&2: To be better off putting it on deposit you'd need to earn that (+DIRT) to make it worthwhile i.e., 6.1%, Such a rate is not presently available. The fact your mortgage rate is variable also adds a degree of uncertainty here.
3&4: Investing or setting up a business (becoming a landlord) will attract a range of taxes and risk. Those tax rates are higher than DIRT rates so your required return well be even higher than the points above. For the possibility of higher returns your definitely have to take on more risk.
You mention becoming a landlord. Search the various forums here and you'll find plenty of them clambering to get out of the market right now.
Unless you're particularly risk averse or there's other info with sharing tackling the mortgage looks your best bet.
3) Make mortgage overpayments of 4.1% interest but interest rates are likely to fall, so it would be better to wait for them to fall and then make the overpayments so you don't overpay interest.
1) I would differentiate between expectations that the ECB will cut rates and if/when that might be reflected in your mortgage rate. Lenders were at pains to point out they didn't pass on the full amount of rate increases when the ECB was jacking up rates. I see no reason to assume they'll be generous on the way down.
2) Interest is calculated daily so you'll get the benefit of overpaying straight away. If rates do fall you'll still make a saving just a little less but I don't see any reason to wait for a possible mortgage rate reduction.
Definitely the mortgage. The 4.1% interest is being incurred whether you overpay or not. Overpaying will only reduce overall interest charged. You’d need to take into account overpayment charges though.
It's even better than that as there are no charges for overpaying a variable rate mortgage.