So basically, assuming it does arrive, it's useless to me unless I pay?

Or can it still work and show me the free channels without paying the £35 activation fee?

Technically they are not in this case as they won't be sent out until and unless you agree to the terms and conditiions of the offer.

According to the OP he got a letter from BT saying they are sending one out and he didn't ask for it. Of course it is possible there is some wording in the T&C that allows them to get away with this, hence my suggestion to play safe and tell them to pick it up or send postage within a stated time period if they want it back. Of course, it is possible the OP didn't fully understand what the letter from BT actually said, no surprise there with the small print I regularly see in so many agreements. For even before I needed glasses when I still had 6/6 vision I still often needed a magnifying glass to read them.

I had a similar letter. However, my understanding of it was
You have broadband, why not upgrade to TV £5 per month with £35 for installation. £199 if returned within 12
months. You have to apply to receive.
I know TalkTalk have sent out the basic box to customers, with a letter.
Anyone have a Youview BT box, what is it like does it work OK? Cheap PVR for 1 year subscription.

Humax HDR-2000T £169 is what my parents got and I was surprised how much of an upgrade compared to their old box - much faster.

So if after the 12 months you can cancel the £5/month you can get a similar ish spec box for £95. Plus who knows the extra online stuff in the YouView may prove useful.

Alas not had a YouView box to compare, and the TalkTalk one is known to be the slower of the two devices out their.

That would make more sense but sense is not something I routinely associate with BT