once this Tronsmart is set up I can buy and program a remote control to use with this like regular media player?

yep.

Any Windows compatible remote will work.

You can use cheap presenter ($6.2 via mobile app) or more advanced remotes

http://www.aliexpress.com/item/Brand-New-2-4GHz-Wireless-USB-PowerPoint-PPT-Presentation-Presenter-Mouse-Remote-Control-Red-RF-Laser/32230352058.html

Does anyone have experience of either of these two options for a media player: raspberry pi 2 with Kodi or the nvidia shield?

Forget all this shit. Only normal Windows 10 players will be problem free, tested by millions of people.

As I said get something like this

http://www.aliexpress.com/item/Original-Tronsmart-Ara-X5-Plus-Windows-10-TV-Box-Intel-Atom-Cherry-Trail-Z8300-Quad-Core/32637954158.html

or if you like fancy stuff and do not care for USB 3.0

http://www.aliexpress.com/item/Newest-8-9-Inch-1920-1200-PIPO-X9S-Mini-PC-Windows-10-TV-Box-Cherry-Trail/32630884727.html

if you want only wired network connection (it was Wi-Fi but do not count on quality on tiny wire as internal antenna)

http://www.aliexpress.com/item/Wintel-Pro-W8-PRO-Z8300-Windows-10-4K-MINI-PC-2G-32G-802-11b-g-n/32616539207.html

Actually, I would recommend getting a fixed screen if you can. Less wrinkles. I'm in Australia, don't know about uk screens but here you can get a 110" fixed screen for around $400 AUD.

yep...windows w/vlc.... the player of choice. You can also get a blu ray with usb input, but it isn't nearly as flexible. My personal preference is picture is far more important than sound. I've got a 5.1 but the image quality is what makes the experience.

Hmmm - I'm hoping a large, smooth white wall will be good substitute for a screen :) I'll checkout decent subwoofer options to work alongside the Audioengine speakers. Any suggestions on wireless connection for the speakers?