Welcome, Sadey!
First, I would look for problems like too much shade, poor drainage--or the opposite: dry, sandy soil--heavy foot traffic, especially from kids or dogs, poor soil and no feeding or addition of compost, that sort of thing.

Welcome to GoY, Sadey!
You need to make sure you have the right lawn seed for the situation - there's quite a choice out there, and most conditions can be catered for. Secondly, in addition to everything Tugbrethil has said, and expanding on it a little, would it be possible to dig the area over before trying yet again? The soil could be very shallow or compacted, or just poor, and good preparation could be the answer BEFORE sowing, then assiduous care - watering, etc., especially in it's first year so it can establish itself really well, might be the answer.
Good luck! Let us know how you get on.

When you've 'sown seed' previously, how have you prepared the ground before doing it? Or did you just sprinkle the seeds onto bare patches, without doing anything else, and leave it to get on with it?

had turf laid about 2yrs ago I don't think the soil is that good underneath and yes I have put seed on there raked it in but it still the same always :(

Thanks for replying guys:)

If you want to seed bare patches, it's necessary to get the soil in the area to fine tilth at least an inch deep, level and then sow the seed.
But if you had turf laid, what happened? Was the ground prepared properly prior to the turf laying? Is the lawn in shade most of the day? Do you have dogs?

Just so you know, Sadey, you can "answer your own question" to communicate with us--we will be automatically notified, and you won't have to edit your question...unless you want to send us pictures! : )
Re soil improvement: there are two main ways, the easy but slow way, and the quick but hard way.
The quick way is to strip off what is left of the turf, apply 3 or so cm of compost, and till that in 15 cm deep, possibly along with a slow release fertilizer like Growmore. If your soil is a very heavy clay, you can also add coarse sand and gypsum (or lime) then. The main disadvantage is that that will be hard on the roots of any trees growing in the yard.
The easy way is to apply a cm deep layer of compost twice a year, and gently rake it into the turf and exposed soil. Over several years, that will decay and support scads of soil organisms--including earthworms--which will till the soil for you. You can reinforce that effect by using an organic fertilizer on a regular basis, instead of weed and feed.
Once the soil is better, the seed should take--barring excessive shade or dogs, as Bamboo says! Remember that unless the rainfall is unusually frequent, soft, and regular, you will need to use the hosepipe regularly for a month or more to start seed.
For shade, look for seed of shade tolerant grasses, such as Poa trivialis, or turf-type tall fescue.
For dogs, keep them off the section of yard that you are seeding for at least a month after the seed comes up. Also look for more wear tolerant and self-healing grasses, such as the rougher forms of bluegrass, or creeping fescue.
Good luck!