Later, once you are back in Warsaw, you will have a chance to see how different the 2nd World War looked in this part of Europe. Such “double” trip during 1 holiday may be a perfect way to discover this complex history! Because of the fact, that those days there are lots of flights from London to Warsaw, it will be easy to buy flights for most convenient date and time . Thanks to this, such trip will be quite easy to organize.
Another idea for unusual holiday is to go to Stockholm in order to attend as lots of festival as cultural events as possible. During the summer there are many events like this in the city! There are big as well as already famous events (as for example Stockholm Culture Festival), but also plenty of small, alternative events in different parks and even on the street! It is not hard to find info about them on the internet, so finding them will be easy too (much more you can read at this address). Additionally, there are plenty of cheap flights Stockholm, so such trip could be totally affordable and does not have to ruin your budget, even if your budget is extremely limited.