Phone, I think you have Mugil cephalus, and possibly some others. We have Chelon labrosus, Chelon ramada and Chelon auratus. That's your flathead or striped mullet and our thick lipped, thin lipped and golden grey.
So, no, I don't think we have the same species, but the weird thing is that the same species we have here are hugely easier to catch in other parts of Europe. I caught them by the dozen on childhood holidays to the Mediterranean, which was as you say, a blast, yet those here are like ghosts. Very strange.
I spent many years trying to catch, even hook, the mullet in the Clyde estuary while visiting my in laws in Irvine. My hook up rate was very poor, and I only managed to land a couple of smaller ones. In fact during the hot summer of '75, I got to touch more without a rod. They were that numerous that at low water, hundreds of dorsal fins could be seen close into shore. Not being one for sunbathing, I used to wade out, (it's a very shallow, gentle sloping beach), and the fish would part, and swim behind me. I would lie on a lilo, and slowly drift towards a shoal, then slide off into the water, and try and catch them by hand. I never did anymore than touch the odd one. A few years later I was on holiday in Malta, and walking along a small stretch of jetty, saw a young lad fishing with a pole, fixed line, a bottle cork float, and what looked like bread paste. As I walked over he landed a fish of about a pound and a half. I asked him how he was doing, and he lifted a cloth from a large bucket, to reveal a dozen or so similar sized mullet. I watched him catch another half dozen, on the bread, and about a size 8 hook, before he packed up. He was fishing to supplement, the family diet, not for fun. I'd fished almost the same, a bit more refined, as him, and really struggled in Scotland, but this seemed more like fishing an overstocked commercial in comparison.
I remember that the number of mullet around at that time caused the local angling club to change it's rules. They used to fish fly only matches, on their stretch of the river. The downstream stretch ended at a weir/dam that had a section cut out of the middle to allow the run of salmon and sea trout. One young angler fished just above this dam, at high tide, and landed nearly 20lb of mullet. The rule book only said fly only, and no salmon or sea trout, not a mention of mullet. He was awarded the match, but the rule book was soon amended.
Angling is more than just catching fish, if it wasn't it would just be called 'catching'......... John