Mum2SamandAlex,
Is the place 3 hours away your DH's normal place of work? If it's his normal work location then sorry, no, he cannot claim travel and accomadation as expenses. Tax rules will only allow employers to reimburse genuine business expenses, and how far away from your work you choose to live is seen as your own choice. It would be seen by the Revenue like my employer paying for my travelcard and calling it expenses...
An employer can choose to pay those costs as part of someone's salary package, in which case they would be subject to tax, etc, as normal. Employers sometimes do this if (i) they move people to another office and want to keep them, in which case it's usually for a transition period; or (ii) if someone is very, very specialist/senior, highly in demand and it is negotiated as effectively part of pay. It is rare otherwise, and it is always the employer's choice whether to offer to pay or not.
If your DH is working away from home for some reason - e.g. a short term project at another office - then it is normal to reimburse expenses. As Custardo says, it is not obligatory and you have to look at his contract. You will probably find what they are willing to cover. As she says, most employers will have rules - e.g. about how much a dinner can be, whether alcohol can be included, what class of train travel is acceptable,etc.
HTH. Sorry it probably isn't the answer you were hoping for.