She can do so. The trust doesn’t kick in until you die so, if your house is worth £500k and you split it 50/50, you each have a £250k share of the house. She can move to another £500k house using her £250k plus your £250k and the kids will only get your share when your wife dies. However, if your wife moves to a £400k house, she uses her £250k and £150k of your money leaving £100k left over. That goes to your kids or whoever you are leaving it to. At no time can your kids/trustees take what either of you left to them until you die or, in the example I’ve given, move to another house smaller house with money left over.