It's just business. (Score 1)

Do the right thing. Do what is right for you and your family at the particular point in time of your life. There will always be projects, and if your current company treats you well, that's great. As you know, especially in the UK, there are lots of layoffs happening. You may be totally loyal to the company, yet the company may lay you off. It's just business. And it will be out of your control. Training the 'juniors' is a way to help hand down your skills to the cheaper staff. Outsourcing programming jobs is getting easier, and your job may end up being outsourced in India or China. On the other hand, more money, closer commute, similar type of job - these are very attractive attributes of the new job. You will save 45 minutes in commuting time. As you put it - a massive difference in your life. DO IT!