UK economic growth

[Thankyou4calling]

I saw today that the UK economy grew at 2.5% last year, it was said to be the fastest growth since 2007.

My query relates to how this figure is arrived at.

Suppose you have a year of decline (recession) as we have had and then record growth, is this measured against the year of decline in which case we may not be back to where we were and that is without including inflation.

With our total population 10% up on previous and inflation at perhaps 3 or 4% isn't 2.5% of total growth actually a decline in real, like for like terms or am I missing something?