Where to go next?

I've been on the MSE path for a few years now - but wanted to check in and see where else I could improve my position. Currently early 30's, married with children. 40% tax payer and main breadwinner. Spouse is a basic rate tax payer.

1) Debt - a mortgage (see 2)
2) Mortgage - overpayment maximised for this period.
3) Pension - contribute a reasonable amount. Forecasting to breach lifetime limit in my mid 60's but that is obviously based on 30+ years of assumptions so may be a red herring? Any thoughts on this appreciated as I intend to increase contributions from time to time which will compound the issue.
4) Cash - Santander 123 only saving account. Currently got around £25k. Probably only need around £15k in easy access.
5) Investments - around £40k of Vanguard 80% in an ISA, aim to add around £10k a year to this. Hoping to not need this for around 20yrs, then ideally draw down income rather than capital.

I'm happy to continue to drip feed into Vanguard as the meat and veg of my overall strategy, but it feels like I'm missing the middle ground for medium length/risk savings for things like moving house, cars etc. Just now for me It's either cash, or S+S. What options exist for this?

More exotic suggestions - I'd also be interested in adding some spice if it's beneficial and completely legal. My current thoughts were contributing to my wifes pension pot to take her out of a tax paying position would save us 20% tax up front, adding a reasonable amount to peer to peer lending (how does this work for tax purposes? Can I wrap in an ISA? Otherwise I will break through savings limits quite quickly eroding the benefit somewhat), EIS or other vehicles - I've little knowledge on these other than they exist at this point. Any suggestions here or further resources/reading appreciated.