OP, ignore Hartley and other pp suggesting that spousal maintenance is unlikely or in some way immoral. Thank goodness the law doesn't agree, and recognised that it is sometimes necessary in order to achieve parity on separation.
I got SM, as did several close friends, but my solicitor advised that it is only appropriate in marriages of 20+ years and where there is a significant disparity in income.
You need to find a good solicitor who can talk you through this, so you're not receiving conflicting advice on the internet - it will be money well spent.
All of your assets will be put into the pot and carved up. It may be that you would prefer to take a greater share of assets instead of SM, as that gives you the clean break.
House £150k
Holiday home £30k
Pensions £180k
Savings £50k
Car £65k
The starting point is 50% (£237k).
If you are thinking of asking for £500pm SM for say the next five years, that is £30k. You may prefer to take that money now, by way of a 60/40 or 70/30 split.
A good solicitor will be able to tell you what is usually realised in your area, in your circumstances.
If it were me, I'd be looking at taking the whole house, 50% pension and 50% savings in order to forgo SM (£265k).
He can use holiday home and 50% savings as a deposit on a new property, using his high salary to achieve a mortgage. With the car and pension this represents £210k and seems fair.
The only fly in the ointment in the car, if it's on a PCP or similar it actually represents a debt rather than an asset.
Talk to a solicitor and then present your suggestions to your dh. If he's amenable you can do it yourselves and save a lot of money.