As an actual qualified HGV driver working for agencies for fifteen years until recently, the above is complete bollocks ...
You work for an agency, you're an employee having tax and NI deducted, getting holiday and sick pay same as any other employee in any other industry. HMRC's predecessor Inland Revenue closed all the various loopholes decades ago, the only way 'round 'em is to set yourself up as a limited company, agency HGV drivers aren't paid enough for the extra costs.
You're a foreigner working for a British agency, you're still an employee having tax and NI deducted, getting holiday and sick pay same as any other employee in any other industry. You want your tax and NI back when you return to your foreign country, you have to prove to HMRC you're entitled, bugger-all to do with the agency.
Working for agencies is actually better-paid than working for most companies, simply because working for most companies, you're salaried - you get the same money irrespective of the hours you do; otoh, agency drivers get paid minimum 8 hours then time-and-a-half for anything over. In the time I was first a 7.5t and then an HGV driver, I had one salaried job, for three months ... Agency driver, you can have as much time off as you want (albeit unpaid after your holiday's used up), when you want. When I lived in Kent, most of the dads had high-powered jobs in London ... I was one of a handful of dads as school sports days, Christmas concerts, blah. You can't buy that with a big London salary ...
There is a general shortage of HGV drivers because of several factors:-
. Back in the naughties, it cost me a grand just to get my Class C (rigid HGV) and that was using a small 2-man company that wasn't turning over enough to pay VAT. It would've cost me another grand to get my C+E (artic. or wag-'n'-drag) ... to be paid another £2 an hour ... Otoh, if an agency driver sticks with the rigid licence and spends any extra on crane licence, Moffet (lorry-mounted forklift) licence, dangerous goods licence, he can pretty-much double his/her hourly rate.
. If individuals aren't stupid enough to pay for a C+E licence, it's down to companies. The last time the transport industry had a driver crisis (well, bigger than the standard normal crisis), back in the early tens, is when they first hired loads of mainly Eastern European drivers. By-and-large, the road haulage industry won't pay to train drivers. The basic problem is, same as any industry, despite paying (several thousand pounds in this case) to train someone, employers are legally prevented from charging that person anything if, at the end of the training, the person either doesn't want to do the job, or is lured away to another company that doesn't do training and pays more money. Now we're out of the EU, the biggest favour HMG can do the whole of British industry is put some legal reality checks around the Free Movement Of Labour principle.
. The other problem with HGV driving is, for what the job is, the money's shit, even if you work for an agency. The root of that is, absolutely everything moves on a lorry between coming out of the ground and reaching you. So, if you want to increase HGV drivers' salaries significantly, it's ultimately coming out of your and my pocket. Unfortunately, the road haulage industry is too fragmented to manage that (the Road Haulage Association is a figurehead, not a leader or commander). So the industry stumbles from crisis to crisis; occasionally the crisis becomes deep enough it impinges on broadcast news producers' consciousness, then it's put in front of the masses on the idiot's lantern as something new. If anyone thinks all the unctuous and earnest hand-wringing by politicians and broadcast news "transport correspondents" is going to change anything fundamental, you're significantly more stupid than you look ...