This calculator from MSE may help you consider your options.
www.moneysavingexpert.com/mortgages/compare-mortgage-rates
The reason that lenders like longer term fixes is that they know that they will have your business for that length of time (as there can be exit fees if you decide to change mortgage during the fixed rate period).
Recently the new Governor of the Bank of England stated that he does not expect to raise the base rate until unemployment drops by a very significant amount (I forget the actual figure), which has given more lenders the confidence to offer longer term deals.
In my case it made me look at Tracker mortgages, these often have lower rates than Fixed but obviously will go up if the base rate changes. I decided to look at how much the base rate would need to change for me to be paying the same as on a fixed rate mortgage and I would need the base rate to change by more than 1% before I was even paying the same as the fixed rate payment. This allows me to budget accordingly and make overpayments in the meantime.
It really depends what you want from your mortgage - do you prefer to know that you will have that same outgoing every month for 5 years? Or do you see your circumstances changing before then and may want the flexibility to change your mortgage accordingly?
There are also some fee free mortgages out there currently, no set up fee, no exit fee and some allow overpayments (if you have any spare money).
Like others I'd say have a look around several places and see what there is on offer - also remember not all lenders are included on comparison sites so there are some you are better off checking with independently.