[susan53]

First of all, distinguish between "silent letters" and elision. A silent letter is a letter in the written form of a word which is never pronounced - so in the words you mention in (1) the "h" is a silent letter. The pronunciation of those words in a southern British accent would be :

1)vehicle /ˈvi:jɪkl/; 2) Durham /ˈdʌrəm/; 3) Pelham /ˈpeləm/; 4) Fordham /ˈfɔ:dəm/

In a northern British accent, Durham would be /ˈdʊrəm/
In most southern British accents the rhotic /r/ is not used. So the pronunciation of I worked hard (including the /h/ elision but ignoring other potential changes which would occur in rapid connected speech) for the moment would be: /aɪ wɜ:kt hɑ:d. Changes I would make to your other transcriptions to represent them as they might potentially be spoken in rapid connected speech in a standard S. British accent, would be:

He broke his arm /ɪ brəʊkɪzɑ:m/

Tell him to come /'telɪm tə 'kʌm/

I told you to give her the book / ʌ tɔ:lʤə tə gɪvə ðə bʊk/
Is this his house? /ɪz ðɪs ɪz haʊs/ (the /h/ in house might also be elided in certain varieties - eg London)

Anything would have been better /enɪðɪŋ wʊdəbɪn betə/

He could have done much more /ɪ kʊdədʌn mʌʧ mɔ:/(In N.British /ɪ kʊdədʊn mʊʧ mɔ:/)

It should have been you /ɪt ʃʊdəbɪn ju:/ (The pronunciation /ʃʊrəbɪn/ might be used in a N. British accent)

I know her brother /ʌ nəʊwə brʌðə/

It must have been love /ɪp mʌstəbɪn lʌv/ (In N.British /ɪp mʊstəbɪn lʊv/)

I might have been an architect /ʌ maɪtəbɪn ən ɑ:kɪtekt/

vehicular : /vi:jɪkjələ/

Some accents would also substitute various allophones for the /t/ sounds - eg the glottal stop in a London accent.

I'll answer your questions another time.