Is it on the roof now or is it an indoor aerial near to the TV?
My aerial only gets a good signal at the top of a very long pole attached to my chimney, same for my neighbours. A loft aerial would be no use for me
Unless you are fairly close to the transmission source, you are likely to need a masthead amplifier to increase the signal strength – your aerial installer should be able to advise.
Many on these masthead amplifiers are limited to a gain of circa 20dB (only x10) - you are likely to attenuate the TV signal by more than this by placing it in your loft.
Of course there is nothing stopping you leaving the outdoor aerial where it is if things don’t work out with the loft aerial.
If you can easily get into your loft you could install it yourself, saving lots of money.
Would half it at least in my opinion. Bought a huge aerial once to try in the loft, worse reception than the old small one on the chimney. Wasted my cash.
^On the other hand, I have a loft aerial which gives better reception than my roof-mounted ever did. When auto-tuning the TV and DVD recorder, all the signal strengths are "10".
But, I am about 15 miles from the transmitter!