Best way to save/use £50000

The usual answer to these types of questions on this forum , is it is impossible to give an answer without more info about your overall financial circumstances and goals .
If you wanted to spend/use the £50K then that is up to you what to spend it on .
Otherwise you could save it in a no risk savings account , with low returns . Or invest it for potentially higher returns but with some risk .
If you wanted to do the latter then you can do this outside or inside a pension wrapper.
Inside a pension you will get immediate tax relief but there will be restrictions on how you can access the money and you will probably pay tax on that.
If your husband is a higher rate taxpayer then using a pension is usually the obvious way to go . If he is a basic rate taxpayer it is more debatable.