In practice we already have agreement on the intelligence sharing and air traffic along with most of the detailed stuff so the big problems are trade and customs. Two main effects:
I thought that the intelligence sharing hadn't been confirmed yet? I'm guessing that under the auspices of Interpol it will continue to work somehow but not as well as currently. The good news is that if you get a parking fine in Amsterdam it will be less easy for the Dutch government to get the money from you (although you may discover that if you re-enter the country in your car in future you get held up at the border.)
Milk prices seem likely to go up because farmers currently don't get enough money for milk, per liter, compared to production costs. IIRC that is down to EU regulations and subsidies. When the subsidies vanish and aren't replaced by the UK government (IIRC they have confirmed that they will not be replaced one for one) the price of milk will rise to its correct market price. Which will be higher than it is now. It remains to be seen if the UK has enough capacity to meet demand.
Meat: yes, you will be able to source (probably also online) from farms. You may have to already register as a customer if you want to ensure you get your supply (as some farms i have heard of are doing) and you may also find that the price of your beef/chicken/lamb increases to its correct market level. Which may not be much higher than currently if you are buying directly from a farm, more so if you currently buy at Aldi.
fruit & Veg: same. There may be less variety to begin with and it may make us all more aware of seasonal produce which is no bad thing. I wonder what the market is for swedes though.
(the good news for flat dwellers is that tomatoes grow well on windowsills all year round if you're careful). Things like pineapples, mangoes and bananas will depend on how they are shipped from the country of origin. If they are containered into Europe chances are they dock in places like Rotterdam, Hamburg and Trieste and are then transported either overland by truck or train, inland waterway or air to the country of destination. So in theory not too bad, but if there are truck delays in the Netherlands, Belgium and France - and again in Kent, who knows? - it may lead to rotting fruit/veg. It will depend how they are packed. Either way, additional time/effort on the import may add to the price.
Pharma - no idea. I haven't really thought about it. Insulin isn't produced in the UK afaik, but also other medications. Euratom is also one of the things that seems to still be up in the air.
Then there are things like the NHS. Yes, it will, in theory, be easier to get nurses, doctors etc from African, South American etc countries. However there may be some reluctance to come over without cast iron guarantees about bringing family, and residency. Again, in theory this should put up the price (wages/salaries) of such staff making it easier for outsiders to meet the threshold for coming over, and also make the jobs more attractive for the British. Time will tell.