if you have skills try to make service site will gain a lot of money
use your money on place that you have more knowledge on it
if not have hold it only
I think If your intention is to hold it it will be the best choice you can. Hope you get the answer and benefit you.
Why not on both £ 250 on bitcoin and £ 250 on the ethereum is safer in that way and more practical in my opinion. You can be sure to profit from it rather than putting all in one investment because they are performing well at the moment.