For the birds a bang up place to get personalized underwear is at GettingPersonal.co.uk.  They have a Personalised Christmas Underwear Print which is bright red so it would also work for Valentine's day as well. I've created take two pictures of prints below the one on the left is the default and the second is inserting RedValentine.co.uk for the personalization!

What can I put on my print
Single Name - e.g. Suzanne or William
Full Names - e.g. John Smith
Messages - e.g. Best Wife! or Top Chap!

We are still searching the internet for places to find personalized chap undies but have yet to find a decent location. If you do find anywhere please leave us a message to let us know!

If you're looking for more personalised gifts we also recommend A1Gifts.co.uk.

If you are going to order a gift we recommend Getting Personal. It is the most popular personalized gifts in the UK. However selecting a personalized gift is only the first part of your Valentine's Day present. The second part question is:

What do you put on the personalized gift?

This question is not easily answered as it's dependant on a few factors.  However, here is a little guide to hopefully help you pick the proper thing to write.

What stage your relationship is in will depend on the wording for your gift.

New relationship: If you are in a fairly new relationship then putting "I love you" or something of that nature is probably not the best option.  You should consider using something like "Be my Valentine" or "Will You Be Mine?"

Long loving relationship: If you've been in a relationship for a while then using a term like "Be my valentine" might give off the wrong impression.   Instead opt for "I Love You, will you be my valentine" or something a bit more personal.

What gift you select or make will depend on what you write.

Practical and Useful: If you've selected something practical and useful to personalize (like a coffee mug or mouse pad) then you don't want to make the writing quite as personal.  Something like "be my valentine' or 'I love you' will be sufficient in this case.

Something more personal (like a calendar): You can customize this and write whatever you would like on this.  Possibly a poem if you're linguistically inclined.

Whichever gift you select to personalize be sure to put lots of thought into what to write on the gift.  That's what personalized gifts are so special.  You must select the proper gift AND the proper thing to say.