Done many TV and film jobs as "background artiste" or extra:
1) you generally won't get employed unless you are with an agent, who will want 20% of any fee.
2)The money is peanuts;.... TV is around £80 a 12hr day, films can be as little as £50 a day.
3)You will be expected to provide your own 'costume' if doing something like Emmerdale but it is provided for period stuff.
4)You have nowhere to hang your 'costume' and nowhere to change, except behind the set: men and women together, young and old.
5)You are treated by the company as the lowest of the low, having to eat after the crew and 'actors', often in a freezing cold old bus or similar.
6)It involves MUCH waiting around (hours at a stretch, sometimes) sometimes without anywhere to sit, or any lavatory facilities near by.
There is more but I think you get the idea.
I once walked off a set for a film having turned up 25miles from home at 6-30am, changed into costume and then been bussed another 5 miles to the location, only to find that the 'wrap' (end of filming) would be 9-30pm and that the fee was £50 all in!
I worked out that I'd be working for less than £2 an hour, once I'd taken my agents fee off and expenses.
I queried the fee but was told "tough", so got changed and went home.
Unfortunately, there are many 'amateurs' out there who would gladly pay to be on TV or film and that ****s it up for anyone actually wanting to make a living out of it.
The oportunities are few and far between too so most people would be lucky to get a weeks work in a month.
Best of luck and kind wishes.