I'm 'learning from' every book I get my hands on (including Wilding's). Just dip into one or other of them now and again. But to the point: I found the Answer Keys to Books 2 and 3 of the Wilding set somewhere on the Internet about a year ago. Suppose more copies will surface eventually.
This kind of thing:
Book2, Ex. 5:
1. Beautiful country houses were being built in Britain.
2. Unless our allies hurry, we shall not be freed.
3. Great power was wont to be entrusted to the consuls.
4. If we resist, Caledonia will not be conquered.
5. Sometimes the Romans were helped by the natives of Britain.
1. Villae pulchrae in Britannia aedificabantur.
2. Nisi socii nostri properaverint, non liberabimur.
3. Magnum imperium consulibus mandari solebat.
4. Si restiterimus, Caledonia non superabitur. (Sean Connery?)
5. Interdum Romani ab incolis Britanniae iuvabantur.
I find one can learn a lot from comparing answers with questions, no matter how surrealistic they are.