NB WE DO NOT WANT PVC REPLACEMENT replacement window for a bay

We have moved into a house with small bay windows. The existing windows are unattreactive as the frames are very thick-so the glass is relatively small. There are presently five panes of which two open and five smaller overlights, of which one opens. The whole bay is about 2.5 metres, each window is about 50cms wide, is a bow and about 4.5m high of which the top lights are 37cms square My question is should we consider aluminium or wood replacements-and how much should we budget.