Ok, so, in round numbers, you are making a profit of €20k per annum before tax on the rentals (ignoring price appreciation/depreciation). Let's call it €10k pa after-tax.
If you were to borrow €400k at, say, 3% pa to buy your new home, the interest cost would be €12k pa. That's obviously higher than the net, after-tax profit on the rentals.
No brainier for me - sell your three properties and buy your desired home mortgage-free.
And then start maximising your tax-relieved pension contributions!
You're actually in a great position financially. You just need to be careful not to fall into a "mental accounting" trap (eg this property is for Mary, this one is for Johnny, etc). Money is money at the end of the day.
Hope that helps.