level threshold or not - which way to go:
in london, and therefore less exposed areas, a level threshold can work - but we always advise clients that there is more increased chance of rain being blown into your lovely new extension. there are some more better considered suppliers of bifold doors, with really nice integral drainage etc - but if your children are as obsessed with the hose pipe and buckets of water as mine, then expect some water to creep if not gush in with a level threshold. a step down from inside to outside overcomes a great number of issues. on cheaper bifolds the water can collect in the bottom track - and the builders will simply drill holes to the outside which will quickly block.
regarding tiles: you want to make sure that your tiles are not slippy when wet (R9 rating). you can get the same looking tile, but with different slip ratings - and a great deal of tiles, from many suppliers have this as standard now. You should be looking for slip rating R11/12 minimum if you dont want to go rse over it when popping out to grab the washing.
they will look slightly different though, and pick up/show/hold dirt more of course, as more abrasive to touch.
we can recommend Domus, World End tiles, Porcenalosa etc

I would second Rak.

One word of warning though...I wanted my indoor and outdoor tiles at the same level but every single person I spoke to said it wasn't a good idea because water might seep under the doors (no idea whether this would happen in practice). We also had a bit of an issue with access to the drainage so that we could clean it out and settled on a thin strip of tiles that isn't grouted down.

Hi,

I have not heard about Valverdi tiles but there are so many tile companies.

Rak tiles do good indoor & outdoor tiles and are reasonably priced!

Hi there

Probably not what you are looking for but my husband and I are just starting up an old reclaimed Spanish tile company. We are about to import a load of old reclaimed ceramic tile.
If you're interested at all give me a shout!
Emma

Hi

We are putting bi-fold doors on our new side return and like the look of the same tiles inside and outside. We are considering getting Valverdi tiles - does anyone have any experience of these? Or have any companies that they would recommend.

Many thanks