The state pension of a deceased man is not transferable, in whole or in part, to his widow. Private pension schemes will have their own rules, specific to each scheme, about whether pension benefits are transferable upon death.
If you return to the UK from abroad you will get the full state pension if you've previously accrued a sufficient number of 'qualifying years' of National Insurance payments. See here:
http://www.direct.gov...tepension/DG_10014671
The basic state pension, for a single person, is currently £97.65 per week. However (irrespective of whether you qualify for the full pension or not) you would be guaranteed a weekly income of £132.60 per week. (If you didn't get that much from your state pension and any private income you might have, the deficit would be made up by Pension Credit. If you're over £65 the guaranteed figure rises to £153.12 per week):
http://www.direct.gov...tatePension/DG_188551
Chris