I’ve just taken on a 9 year old old tyme bulldog and he seems to have a few skin issues. His back is lumpy and the hair is raised. His ears look a bit dirty and  crusty. His back legs seem to have what look like pressure sores. He doesn’t seem to be bothered by it and doesn’t scratch or rub himself. He’s on Lidl dry food at the moment and I want to switch to a grain free kibble. What types are best for dogs with skin issues

Well for starters, NO CEREAL-BASED FOOD!!   Choose something that lists meat, or perhaps better, fish as the first, main ingredient.   You won't see a vast improvement, most likely, for some time while the system gets rid of what's not been suiting this poor lad.   Your vet should be able to prescribe an antiinflammatory to calm his system down and a decent shampoo too.     For a fish diet, I have used Arden Grange Sensitive (fish and potato) to good effect and my two are now on their Salmon and rice diet - also all good.

something like yumega for extra omega 3 is useful for skin. vets do one called nutramega . I would always recommend raw feeding but if not as mamabas says grain free and high meat content with as few ingredients as possible. eden or akela are considered good .
Depends how things go but you may have to look at allergies either to food or environment. He might just need a better quality food of course

I was thinking of giving him
Nature diet which I feed to my chihuahuas. It’s grain free and they do a sensitive one which is salmon and rice.

> It’s grain free and they do a sensitive one which is salmon and rice.

Rice is a Grain.  So not that one.

The food he is on is likely very poor quality in that from memory there is only about 4% meat content in those budget supermarket brands.

So grain itself may not be an issue, but to get his skin better avoiding it will do no harm and probably more good.

> Rice is a Grain.  So not that one.<br />

True - but my reason for using AG Sensitive and now Salmon and Rice was not because of a skin condition, but a digestive problem post-Giardia.

I would agree with @furriefriends and suggest a raw diet.
As also mentioned by @mamabas, a grain free kibble (remember that Rice is a Grain too!) Eden is very nice and Bentley's too. Neither products are cheap but because of their quality,less is needed to be fed.

They do a grain free nature diet so I might try that. It’s just easier for me to use the same food as I already use for the others