Right now, I have to disagree with your friend. If you can find a job in engineering, this will provide you with greater stability and security. The Reading area and "M4 corridor" have a high concentration of hi-tech companies and employers in the hi-tech sector may be interested in your skills.
I do not think you will enjoy a career in consulting if you combine a geographical move with a career shift, add in language difficulties and a consulting lifestyle (you will be away from home for extended periods and will not be able to see your wife). Realistically, I do not think you will be able to find a job in consulting anyway. I do not know your educational and organisational background, and how many visa points you are eligible for. However, from what you have mentioned and the way you write, I think you will find it difficult to differentiate yourself from huge numbers of other candidates and to persuade a consultancy that they should invest in sponsoring a work permit.
You could look at moving into consulting within China first. The economy is reputed to be stronger there than in the UK and there are more consultancies who can take direct advantage of your skills and experience in mechanical engineering. Your people management experience also sounds like it will help you stand out in China as experienced managers (and those experienced enough to advise them) are relatively rare.
In the medium-to-long term, as the economy stabilises, you may have an opportunity to transfer from China to the UK as an experienced consultant. However, the trend is for consulting opportunities to be going in the opposite direction; your wife may be the one coming to you :-)