Suz wrote:

We got a second-hand Pashley Pickle trike on ebay, but looks like it got a
ding in transport: the rod from the handlebars to front wheel has been
slightly bent so the wheel can't turn as the mudguard is catching against
the wheel.

Is this fixable?
And would it mean a dangerous weakness is it is straightened?

If by "rod" you mean either the "downtube" - where the stem
(sticky-forward bit) which holds the handlebars is fixed in, or the
"forks" (the bit which holds the wheel on either side of its axle and
then joins at the top to go into the lower end of the downtube) - I
wouldn't trust the tube not to fail in a potentially head-breaking,
worse-than-just-arse-over-tit-embarassment way. At least not on a
full-size adult road bike on T'Public Highway.

[Pauses to Google for "Pashley Pickle tricycle", tho' not as a phrase].
Oh, it is a kid's trike, then. I still don't see how the "mudguard can
catch the wheel", though. To my mind, any bend in a bike frame which
najjers the steering to that point is the "goodbye frame" moment. If you
find a local bike shop which is willing to straighten it out and claim
its intended user will be safe under reasonably foreseeable circs, you
might let them at it and claim only the cost of that repair from the
ebay seller (who can turn round and claim it from their carrier; but
your contract of sale is with the ebay seller, not the shipping agent).
Otherwise I'd try to reject the sale altogether - since you put this
down to damage-in-transit I'm supposing the seller says it left them in
working, unbent order.