There is NO SUCH THING as a digital or HD aerial at all.
An aerial that differentiates between horizontal and vertical is better.
An amplifier in a indoor aerial is almost pointless. Amplifiers are to overcome coax loss. To get more signal you need a higher or better sited aerial or higher gain aerial.
An £8 aerial will work just as well.
If an aerial in same room (so called set-top aerial) isn't perfect, then you are best to put an outdoor aerial in attic, top of cupboards, wardrobe etc and if that's not good, then outdoors.
£50 on an Indoor Aerial is wasting money and rewarding dubious Marketing.