Basically i have this mod i'm working on that's fairly complicated, however it's been a learning experience and i have left a lot of mess around in many cells where i did not want to edit anything, i know that i can set them to be ignored, but at this point it would just feel better if i could start fresh.

So in effect what i want to do is copy some indoor cells from my old ESP to a new one, is this possible? The old CTRL-C, CTRL-V does not seem to work.

The solution you're probably actually looking for is TESVSnip. It's the standard way, pretty much, to clean out stuff you don't need from your mod. I think there are guides on using it well all over the place. It's had several names in the past, for the different games it was for. All of the programs did the same thing though, went through plugin files, and gave you ability to 'snip' out specific stuff you don't want.

To my knowledge you can't just 'copy' reload, then 'paste' something to a new .esp no. You could theoretically use TESVSnip, to take the part you want, then stick it in a new, relatively clean mod.

You're better off just removing any unwanted changes through TESVSnip.

Thank you both very much, both copying and fixing the ESP up worked fine, in the end i with with cleaning the mod up in TesVSnip and saving it under a new ESP. But man, how did i ever survive without this little program? It makes cleaning so easy, are there any other programs one should have at the ready when using the Creation Kit?

Yup totally possible just using the CK did it myself last week.

Make a new .esp
Open CK with the new .esp marked Active and the check the one containing your interiors
Duplicate the interiors you want to transfer and save

You'll now have a new .esp cpntaining the interiors you want.

I had 7 interiors and there was no one I was going to redo them all so before attempting anything using TESVSnip I tried the simplier CK solution and it works fine.
I duplicated and saved them into the .esp I had that contained all my exterior modded cells, connected the doors and it works absolutely fine.
I've not experienced CTD's that people have been having with door travel either.

Wont that make your new .esp depentant on having your old .esp as a active file in the masters file list tho?

Once you have what you want in the new ESP, save it and close the CK. Then restart the CK and before you reload the new ESP you can delete the dependency in the data window. Just highlight the dependency you don't want and hit delete.

I didn't have to do what Chok3 said.

Just saved with the duplicates. Exited the CK.
Then reloaded the .esp, linked the doors and tested it.

Works fine.

I wasn't sure you would need to delete the dependency, but it is easy to do. Having two ESP files linked together has caused me issues in the past when I need to open one of them in the CK. My guess would be that they didn't end up linked with an ESP master.