Can anybody help? I am new to fly fishing (only a couple of weeks) and managed to lose my spare spool with my six weight line on it. I borrowed a reel with a seven weight line it has improved my casting distance but my presentation has gone to pot. The line ends up in a heap on the water anybody got any pointers.

I don't think the extra line weight will make too much difference, as most beginners do not aerialise a lot of line in the first place. There is a case to be made of using a line a weight heavier than the rod when you first start flycasting. So I would suggest technique may be the problem especially as you say you have increased the distance you are casting; try stopping the line just before the end of the shoot that will reduce distance slightly but should straighten everything out.

As Tony says.

Also ensure that you are 'aiming' the rod tip above the point you wish to land the fly, don't drop the rod tip too low or keep it too high...practice practice practice. If it doesn't work, try little variations, it'll happen!

The most common reason for the line landing in a heap in front of you is not waiting for the back cast to straighten before you start into the forward movement. Very common in beginner fly casters.
Stand with your back foot back a bit so that you can turn your head and watch your cast straighten behind you before you start forward. After a while you will get used to the pause and won't need to watch it.
The other common problem is taking the rod too far back on the back cast. Aim to stop it no further than 1.0 o clock. 12 being straight up.
Practice makes perfect but get your back cast right and the rest will fall into place.
Last suggestion, but if you are even a little bit serious about catching fish on the fly the get one or two casting lessons. The money spent isn't much compared to all of the other expenses and will save you much grief as well as increasing your catches.

Thanks for the advice guys. I have another problem at the mo my may fly seems to getting attacked by other fish before the trout get a chance at it is there any way to just target the trout?

About the only way to target trout when using a fly that has broad appeal to many species would be to fish where trout were about all that was feeding.

A small Mepps?

Salmon roe