sorry for the late reply...
I've seen two types of japanese-style saw at Lidl: one a ryoba-style with a blade length of about 30cm and another about 18cm, the latter coming with two blades of 17 and 22 tpi
I've also used an Irwin 'ryoba' and have a Gyokucho ryoba
Lidl: the large one is a bit disappointing. the 'rip' side is rubbish with teeth nothing like a japanese ripsaw - and I don't use that side. the crosscut side is OK but feels clumsy. I use it for bits of wood I don't care too much about and on site where it might be damaged by hidden nails etc, such as floorboards. it's not up to much but for £7, hey...
the smaller one is a different story entirely. it's only got crosscut teeth but they seem to have no set, so it makes an excellent flush-cut saw. it's very sharp indeed and is very durable. I've had one for 18 months or so and have only used the 17tpi blade but it still cuts very well indeed. it's a great little saw: so good that the next time they turned up, I bought two more, just in case. a friend uses an 'Ice Bear' (aka Z-saw?) flushcut saw that cost £25 and it's not as good as this one. the cut is so incredibly smooth that you'd swear it had been planed - probably due to the lack of set on the teeth allied with the japanese tooth profile
the only criticism I have of the smaller one is the handle. I'd prefer a longer one as I find that helps with accuracy but it's not a big issue
the Irwin 'ryoba': pretty crap. it became dull very quickly - I used mainly the crosscut side - and the handle feels very cheap. the rip side is still good but the crosscut side lost a couple of teeth for no apparent reason. I use it for ripping 'on site' so it's still got a use but it's simply not worth buying
as for the Gyokucho: it's the dog's. it's unbelievably sharp and I love using it. apparently the brand is the standard one used by Japanese carpenters... it's not imported to the UK any more but you can get them via that big auction site. just remember there's an import tarriff
get the small Lidl one. it's great and you won't regret it. for £7 it's a real bargain