My two bits on ήθελα / θα ήθελα / θέλησα:
Verbs expressing a state are usually used in their imperfective forms (present, imperfect, durative future).
Some, notably είμαι, έχω, ξέρω, περιμένω, and πρέπει, lack perfective forms (aorist and those derived from its stem) altogether.
Most do have perfective forms, but those usually express a momentary event, or else the beginning of a state. Thus, κοιμάμαι means 'I sleep', but the aorist κοιμήθηκα usually means 'I fell asleep'. (It can also mean 'I slept and then woke up', as in κοιμήθηκα ως τις δέκα το πρωί σήμερα.) Likewise, φοβάμαι means 'I am afraid', but φοβήθηκα usually means 'I was seized by fear' (at a definite moment): άκουσα θόρυβο και φοβήθηκα = I heard a noise and was scared. But if you just want to say that you were afraid of something during an extended time period, you must use the imperfect: Δεν πολυέβγαινα έξω, γιατί φοβόμουν μην αρρωστήσω = I didn't go out much, as I was afraid I might fall ill.
Similarly, as wanting = desiring is a state of mind, θέλω is mostly used in its imperfective forms θέλω and ήθελα. The aorist θέλησα mostly means 'I was seized by the urge to': Θέλησα να σηκωθώ, αλλά ζαλίστηκα κι έπεσα = I tried to get up, but was seized by dizziness and fell (compare ήθελα να σηκωθώ, αλλά ζαλιζόμουν = I wanted to get up, but felt dizzy, i.e. while I was lying in bed, I did have the desire to get up, but I felt dizzy all the time and thus didn't try or manage to get up.)
This distinction doesn't really exist in English. One says 'I was sick', using the same verbal form, to mean both 'I was ill (during a certain length of time)' and 'I threw up (at a certain moment)'. In Greek we must say ήμουν άρρωστος (imperfect tense) but έκανα εμετό (aorist; this is actually a bad example, because κάνω is one of the few verbs that don't distinguish their present from their aorist stem; the vulgar synonym ξέρασα = 'I puked' is a better illustration, since its present is ξερνώ and its imperfect ξερνούσα.)
Θα ήθελα is yet another story. The conditional mode is expressed by a combination of θα + imperfect (or θα + pluperfect) in modern Greek: αν είχα λεφτά, θα παντρευόμουν = if I had money, I would get married; αν το ήξερα, δεν θα είχα έρθει = if I had known, I wouldn't have come. Similarly, θα ήθελα simply means 'I would like'; it is simply a polite way of asking for something (θα ήθελα έναν καφέ = I would like a cup of coffee.) The aorist can't be used in that sense.
(Θα can be used with the present or the aorist in a different sense, namely to express a guess. Θα λείπει or θα έφυγε mean 'I guess he is away', 'I suppose he has left' -- in speaking e.g. of somebody who won't answer his home phone. Likewise, if a sick person is found lying on the floor, you can say θα θέλησε να σηκωθεί και θα ζαλίστηκε = he probably tried to get up and had a dizzy spell. This is perfectly standard usage, but is understandably much less frequent than θα ήθελα in the sense of 'I would like'.)
To sum up: Greek makes an obligatory distinction between an ongoing or repeated action and an action performed until its completion in the past (έγραφα = I was writing or I used to write, έγραψα = I wrote (e.g. a letter) and was done writing) and in the future and subjunctive (θα γράφω = I will write regularly, θα γράψω = I will write once; να μας γράφεις = write to us regularly, να μας γράψεις άμα φτάσεις = write to us when you get there), but not in the conditional, which is only θα έγραφα (θα έγραψε can only mean 'I suppose he wrote'). With verbs like θέλω that express a state, the perfective (aoristic) forms, if they exist at all, usually express the beginning of that state, or else the total duration of a state that came to an end (as in έζησε ως το 1995 = he lived until 1995, implying that he died in 1995.)
) στο χωριό του παππού μου (accepted as it refers to actions). It isn't expected and accepted in the Greek translation as συνήθιζα if it refers to volition and emotions such as, e.g. I used to want = (παλιά) ήθελα (συνήθιζα να θέλω 