This time it's a proper OO train set. Doesn't look bad, but I don't need one of those.

The Star Trek one is tempting though...,

What is a partwork?

Like the Batmobile thing. A weekly/biweekly/monthly magazine subscription that provides either an item (eg car) or part of an item (eg wheel) with the idea that you learn about the topic whilst amassing a collection (either of say cars, or enough parts to build a car), all at costs far in excess of what it would have cost to buy the collection alone.

FWIW, I used to collect World Aircraft Information Files.

A friend did the horse and stables one. What she got was a really impressive set - and I’d say it was worth the money. I think it depends on what it is you are collecting and what you get out of it. The train set will, IMHO, be pointless as I expect you’ll have a long wait for the loco and power hardware. A loop of track may take a few months to gather together.

I saw some of the Batmobiles going for £15 a piece (without the magazine) in an antiques car collector’s shop.

Years ago there was a build a sailing boat which would be spectacular once finished but expensive to build.

Usually when I see adverts for those the price looks okay, then you see the small print saying it's a discount price for the first few issues. The remaining issues are twice the price mading the final model a rip off.

Yes and they may need 50 magazines to complete the project.

I remember a giant glow in the dark T-Rex bones set my mate bought; it was rendered totally pointless when they gave you the 'skin shells'