There's a technical distinction between a church and a chapel which is not based on size. A church is the parish church1, so therefore CofE2. A chapel can be: a subsidiary space within a church or cathedral, an Anglican non-parish church such as a mortuary chapel or chapel of ease, or else a non-Anglican church. The latter may look odd, but it is tied up with the establishment of the CofE and things like marriages. An older generation in places like Wales would differentiate between "church" (CofE) or "chapel" (typically Methodist).
1) Though a cathedral church is not necessarily a parish church and yet can provide the same facilities for marriages.
2) I think RC common usage follows that of the CofE, but AIUI the legal distinction still applies, so all RCs are legally chapels.