I will try and answer the OP question
X will happen and this will automatically improve the lives of the majority of the people in the UK
Nothing will happen automatically. UK will have to fight for Trade deals and give something in return. Examples mentioned on another thread were:
To make a deal with India UK will have to give more Visas to allow people from India to work and live in the UK. I would have no objection tho this as I have worked in India several times and can vouch for their abilities. A deal with India would mean that UK has a partner whose economy will soon pass that of the UK.
To make a deal with USA and Australia UK will have to allow USA and Australia to sell their food products in UK. I have no objection to this as have worked in USA and never had issue with their food. Where I work now imports many food products from Australia and I have no issues with their food. USA might have an obesity problem, but that it due to quantity of consumption, cheap fast food and the number of all you can eat buffets that are everywhere in the USA. Its a lifestyle choice rather than an inherent problem with the food.
I am not talking about the 'feelings' stuff like sovereignty
Some will have been swayed by such thoughts and the "feel good factor" will almost certainly have played a part in the 2016 referendum result even though it may not bring any material reward.
For example, who has the better life; the Lottery winner who is serving life or the person who is on minimum wage, but can leave their home whenever they feel like it to visit friends, go for a walk, go for a beer, etc. Not a hypothetical example by the way. Look on the link:
news.bbc.co.uk/2/hi/uk/3554008.stm
For some an improvement in quality of life does not necessarily mean more money in their pockets. Freedom counts for a lot.