The third party (the "innocent buyer", so to speak) has no role in the prosecution.
That's a matter between Her Majesty and the accused.
(as I said in an earlier post above, bear in mind that
the person from whom our friend above bought the bike,
might not be the thief).
I am not sure that the court will consider the interests of a third party buyer
in the course of a criminal trial for the theft of the bike.
That said, a third party buyer may well have grounds for an action
to recover his money from the seller.
That's a (civil) matter between "the seller" and "the buyer".
I do not see a scenario where the costs incurred by the buyer
to get it roadworthy can be recovered.
The bike itself still belongs to the person from whom it was stolen.
I would expect that in the fullness of time, the bike,
which for the time being is (potentially) evidence,
will be returned to its owner by police, yes.