I am not quite getting the clear answer I was looking for here, guys, although Ximenean’s post is at least to the point. Is it, in fact, OK to fry (even deep fry) frozen chips that are explicitly and exclusively sold (in the UK) as “oven chips”, or conversely, is it OK to oven bake frozen chips explicitly sold for frying, or will the results be horrible (or even more unhealthy than if they were ‘correctly’ cooked)?
As Ximenean points out (and as I mentioned in the OP) the cheapie brands such as this generally say you are free to cook them either way. In fact, that brand (or other, similar, supermarket economy brands) are what I have been using. I have been deep frying them, but I have not been getting consistent results (sometimes good, but often not), which I think may be due to poor quality control in these very low-end brands. Thus I am considering experimenting with some of the more expensive brands. However, most of the more expensive ones seem to be sold specifically as oven chips, and ones marked as for frying are rare. I want to know if it is actually OK to fry the “oven chips”. (I have not generally liked the results when I have done oven chips the oven way, and, anyway, as I have a deep fryer, frying is much less hassle. I also bought some microwaveable ones once, but they were dreadful, all limp.)
It seems to me that I got much better results when I was in the USA and used to shallow fry, but the “fries” sold there were meant to be for frying. Anyway, I am in Britain now, so I can’t get American brands.
I have also experimented with fresh sliced potato in the deep fryer, but the results were very disappointing, way worse than what I get with the cheapie frozen ones. Anyway, it is a hassle, and I want to be able to do them quick and easy.