You don't say what your daughter's age is, but I assume she is a baby.
How about inviting a couple over for dinner once she is in bed?
Going for a walk to a local beauty spot/castle/park.
Cinemas have early morning showings where babies are allowed.
Go out for a coffee and cake in the afternoon.
Soft play centre for DD with lunch afterwards?
Pub lunch on a Sunday - yum yum.
Go and see something at the theatre or see some stand up comedy. Always a great night out.
Look on moneysavingexpert.com for 241 vouchers and go for a meal out to something like Pizza Express where you both get a chance to get out of the house and have a 'date' without it breaking the bank.
Or how about getting those 2 posh meals for a tenner at home and having three course meal with wine and both get a bit dressed up for it?
How about something like going to a museum or doing an activity together? Hiring bikes, abseiling, llama waking... whatever takes your fancy! Have a look on lastminute.com for some ideas.
Make like a tourist and look at local paper and tourist information for ideas for things to do. There is always something quirky and usually free going on that could be great.
If you are trying to recapture your pre baby days, try to think back to what you did then and do those things!
Good luck....you will have loads of fun!