Pronunciation of double consonants

Solution 1:

In English, double consonants and single consonants are two ways of spelling the same sound; unlike Italian, this difference in spelling does not indicate any sound difference. There are compound words such as bookkeeper where "double consonants" are indeed pronounced differently from single ones, but none of your examples are in this category; see this question.

Solution 2:

In general, doubling a consonant in English doesn't affect how the consonant is pronounced (unlike, say, Finnish). If it has any effect at all, it is usually to shorten the vowel before it, as in "hoping" and "hopping" (/həʊpiŋ/ and /hɒpiŋ/ respectively), which is related to the "silent e" spelling convention.

There are exceptions, most of which have grown up through historical accident. All the examples that have sprung to mind are occasions where "cc" has become pronounced /ks/ for some reason: accelerate, accent, access and so on.

There are also a number of double consonants that aren't really double consonants, where one or other consonant is actually part of a digraph with a completely different sound. @psmears kindly supplied outthink and misshapen as examples; there are undoubtedly more out there.