It might be a bad time to get into property for investment, although that depends on the yield of the property you buy - we could be at a peak in the market right now due to concerns about rising interest rates and a potential recession looming, although you're at an advantage if you can buy a property without a mortgage.
But you also need to think about whether you want to be a landlord and spend time doing repairs or sourcing tradespeople to do them.
Problem with investing would be that if we do have a recession, investment products might not have time to recover before you need the money. But you do have the tax relief, which is an instant boost to your money.
I'd probably split it between a pension, S&S ISA, 2/3 fixed rate savings product as a self offset against the mortgage with the intention of using this money to overpay/pay off the mortgage when you can, some cash savings to help DC with uni or possibly house deposit (some people buy flats for their DC to live in at university and often buy a 2 or 3 bed place so they can rent out the other rooms, so that could be an option worth exploring).
Other things to consider is are there any big purchases that you could benefit from? Home improvement, especially energy efficiency measures like solar panels? Electric car to save on petrol/diesel?
Possibly spend some of it on something like a bigger holiday than you normally take?