English oak can very A LOT in quality. I've seen great quality wood with very little earlywood and an estimated SG of 0.80. On the other hand, I've also seen exceptionally lousy oak with very fine rings and way too much earlywood. This wood was exceptionally brittle and did not want to become a bow at all. In general, I think European oak is rated lower than White oak.
Best case scenario: you'll get 26" of draw. However, I think 24" is more realistically. Depending on the quality of the particular stave that is.