Well to be honest with you it won't look great for a while. If you are going to over seed the best time to do it is in sep / oct time giving the new grasses a chance to take a hold for the big spring flush so your lawn will probably be out of commission for this year. The seeds will grow but your coverage will be average. To identify grasses you need a guide with pics but most lawns are rye grasses. They will have glossy undersides to there leaf sheath and will have a reddish tinge and the leaf will also be folded going into the leaf sheath. At least I think that’s right! If you’re going to seed get to it ! Do it now other wise swallow your pride and empty some dosh out for turf. You can check out http://www.barenbrug.co.uk/new.php for seed selection advice and if you do decided to turf then check out www.turfshop.co.uk
Good luck