The foils will spin faster! Less meditative, but still interesting to watch. It is important that they are bolted to a plinth or base.

No they don't, sometimes they will need a clean, as dust and bird poo can accumulate, but rain helps a lot. The stainless steel bearings at some point will need replacing with years of turning, but these are inexpensive, and commonly available.

I love birds, and it was a concern of mine. Having tested many pieces in my garden, I can confirm they are not affected. Professional ecological advice also confirms this.

The Stainless steel is treated to prevent rust, and provides an excellent finish for many years ahead. However, in coastal areas with a high corrosive salt content, they might struggle. Although not necessary for most environments,  I can construct from 316 marine grade steel if necessary. 

Although the foil 'skin' is only 0.2mm thick, they are surprisingly strong and robust (think of trusting your life in an aeroplane made out of thin metal!) Naturally, falling branches and debris can cause damage, but the foils may require covering, or spraying with car de-icer in very heavy snow and thick ice. I've not experienced this (yet)!

Mostly yes, they sometimes make a faint click or creaking sound as the interlocking layers flex slightly during rotation.

It can be, though often there can be obstacles. Any sculpture purchased will have the option of being personally delivered and installed anywhere in the UK, and potentially beyond.

Yes, though this will be subject to additional expenses / taxes, and will require suitable crating