You can have decking butting up to ground level and level with the doors, as technically the ground level won't change and compromise the DPC. There should not be a problem with rats, unless you constantly drop food that would make it's way underneath the deck. You also have an air brick in the middle that I see, so nothing should be compromising that either. I'd consider digging more of the garden away and stepping down on to the patio level, it will look more spacious.

Have you chosen your indoor tiles yet? There are a few tiles on the market these days that are suitable for both indoor and outdoor. If you have chosen your indoor tiles, would they also be the right colour for outside, and what is their 'cleanability' / longevity for not gathering moss etc ? I think for me, hardwood decking would suit the house as would big slabs.So it's down to personal choice. Smaller slabs may look a little dwarfed outside with such a good size of garden. Slabs will look great sat on top of brick steps. Can I see the outside there being clad in timber due to all the horizontal lines on the plan? If so, then decking would not be my first choice as it would potentially clash with the cladding. You may also end up looking like you have a great big wooden log cabin with the cladding and decking. So, I think for a traditional look, to tie in with the style of house, it would be large slabs on brick to match those in the house already.

I want these on my balcony! I think they look great!

Hi, I notice your post was back in July, so not sure if you still need advice? Anyway, my brother is a builder and he laid decking over my rather tatty patio a few years ago and it really is an improvement. He built a framework a few inches above the old patio, and laid the decking onto that. I notice on garden makeover shows that they sometimes lay decking over untidy concrete structures, so I would imagine the same can be done on your old conservatory base. It’s funny, conservatories are a bit like marmite - you either love them or hate them!