Northern Rock 5% online demand deposit. 100% guaranteed by Bank of England.
This might be worth checking out or ask you own bank for a 90 day money market rate on 100k. Just be careful that you don't need access to the funds before the period is up as you will be penalised in interest.
See the Financial Best Buys forum and www.itsyourmoney.ie lists of high rate deposit accounts on offer and the many, many, many existing threads on mixing and matching multiple accounts to maximise deposit interest.