It would seem that the original registers have not been deposited at Winchester. The guide I have implies that they are held on microform both at Winchester and at Dorset Record Office in Dorchester (Christchurch was transferred to Dorset in 1974).
There is an item listed in the Winchester catalogue:
182M88 Christchurch parish register negatives (1584-1643)
Under reference M67 (fragile film), Christchurch registers are included.
Christchurch
88P/1/1 : christenings, 1584-1590
88P/2/1 : christenings, marriages and burials, 1633-1643
88P/2 : christenings, marriages and burials, 1682-1804
88P/3 : christenings and burials, 1805-1812
88P/4 : christenings, 1813-1838
It also includes Burley & Hinton Admiral.
Microfilm M68 contains these records amongst others:
Christchurch
88P/5 : christenings, 1838-1872
88P/6: christenings, 1872-1875
88P/13 : marriages, banns, 1754-1767
88P/14 : marriages, banns, 1767-1779
88P/15 : marriages, banns, 1779-1803
88P/16 : marriages, banns, 1803-1812
Microfilm M69 is catlogued thus, with other parishes:
Christchurch
88P/16 (part): marriages, banns, 1803-1837*
88P/17: marriages, 1837
88P/18: marriages, 1837-1857
88P/19: marriages, 1857-1875
88P/20 (part): marriages, 1875
88P/34: burials, 1813-1846
*The first 17 pages of this register covering 1803-5 are missing due to damage caused during use. Pages 41 and 42 are also missing
Microfilm M70 includes these records:
88P/35 (part): burials, 1846-1875
88P/ : banns, 1834-1869
88P/ : banns, 1869-1875
Burial transcript, 1682-1804
That's the best I can find.

Nell