I'm looking at upgrading my 2015 MacBook Pro and going to the 2018 model with the new 8th gen Intel CPUs. Only reason really is the battery in my 2015 model is getting weak and I want the TB3 ports so I can revamp my desktop setup with one simple dock rather than the multiple I have now. Would it be worth it?

I am also a little concerned about the sale of the old MB. Will the income from it be taxable? It was a gift so all money from it will be income. This [link removed]after tax tool says I should pay something like £300 tax if I get the price I wanted and it counts as income. Should I be worrying?