Generally builders wont grant any access untill Habitation and CML are granted (mine didnt anyway)... but bare in mind you have 2years to bring up snags... (but i would make sure all your snags are in writing and you have something from the that acknowledges the receipt of the snaggin list)
There's a bit of slightly misleading information here...
I think the confusion comes from the terminology. For clarity:
Practical Completion - the building works are finished
Legal Completion - the point where you hand over the money, get the keys and the house becomes yours.
Charles Church have a policy of not allowing snagging before Legal Completion, but there are a couple of problems with that.
New Build Inspections have carried out a large number of inspections on Charles Church propertis before Legal Completion so their policy is not universally applied.
If they don't allow it until after you've handed the money over and therefore can't pull out of the sale, what are they scared of?
If you reserved the property after 1/4/10 then they are obliged to work with your agent (that is, your snagger). If they don't then they are in breach of the Consumer Code for House Builders
Whilst it is true that you have 2 years to submit the list, that also means that you have to allow access for them to come in and carry out the repairs. That means taking time off work, living with mess and dust, possibly being without heat or water, etc etc. It just makes more sense for them to complete the works before you move in.
Practical completion is the stage where the property is deemed to be safe for habitation i.e fully functioning electrics, heating and plumbing, lights working, kitchen in, tiles fitted, appliances fitted and working, taps/shower installed, etc etc... but at this stage there many still be cosmetic work to do i.e final painting, touch up's, cleaning etc etc...
yes by all means you should be able to inspect the property before legal completion (this would be ur demo visit 5-7day before legal completion) where you can check things like your kitchen, bathroom and flooring choices are all correct, the correct spec has been followed, everything works, water, drainage, heating, electrics etc etc. However at this stage there may still be cosmetic work to be complete (depends how quickly the builders want to handover). But i agree with you, it is a pain in the @rse having to take time off and sit around and wait for builders, but unless you give them unsuppervised access... it will have to be done.
But the point im making is if your getting a snagging inspector (which i asume your paying for) to inspect before handover you will still have to inspect again after completion (whether on your own or with a professional) Ie. If the builders still have a final coat of paint to do they might leave marks on the switchs/tiles... and the property will be cleaned just before handover the cleaners might scratch worktops, mark taps or carpets etc etc...
If it is a legal obligation for builders to work to your schedule I dont know anything about it cuz it certainly doesnt happen... so i couldnt really comment on this.