* Menial jobs were/are normally done in the past by younger more inexperienced people. These were usually done part time while in education. This allows younger people to build basic competency and money management skills. They aren't supposed to be jobs for life and everyone knew this in the past. By constantly importing people from to do these jobs, you stop younger people from building up this basic competency. This stuff is important btw, as I know many people who never had these jobs and had the bank of Mum and Dad pay for them for far too long, they don't know how to manage money.
* A lot of more menial jobs are done by people that are part retired. When I was younger I worked with many part retired people that had a stressful job and moved away and part retired and were on the checkouts out the supermarket, cleaning, pushing trolleys or delivering things.
* A lot of immigrants seem to do jobs like Uber Eats, Deliveroo and other zero hour contract food delivery jobs. If you don't believe me, go to your local McDonalds at 8am on a Saturday morning and every driver picking up food will be a immigrant of one sort or another. These are jobs where people are literally too lazy to drive 5 minutes to the McDonalds drive through on a Saturday morning. I am normally very pro-free market however do we really need to immigrants to do these jobs? I don't use Uber Eats and I have no idea how much it costs, but I think the guy up the road that has a small mansion a Jag and Two Teslas can probably afford to pay a bit more for delivery.
* I am from the South of the UK. If you aren't from London or another big city, London is one of the most horrid places to visit, work. I spent maybe a 4 months working as a freelancer in London (travelling in). People are downright rude, everything is a ripoff. I'd rather be slightly worse off and live here than be "better" off an live in London.