If your unsure just go on a sportive and you will see there is every type of bike you can think of, i did my first one (Manchester to blackpool) on a £80
Halfords Apollo mountainbike and really enjoyed it even through i was one of the slower ones and not once did i feel unwanted and unloved as everyone goes at there own pace and it opens your eyes to what is out there and what 60 mile ride is like for you as a rider.
Fast , Medium & Slow all sizes , ages and although they get a bad press on here due to the cost they do a service of getting people interested into going on and venturing further afield unsupported.
I have found getting out and cycling is the joy and to much is written about the pros and cons of each event , if you wana pay then pay if you dont then dont ,, at the end of the day whats £20 ,, its less than going on a Saturday to watch 90 mins of misery watching your local team kick a bag of wind around a field.