newbie needing advice on new bike

Sounds like Mr Bike Shop is succeeding at up-selling you - I agree with him, although for different reasons. Nice bikes, Tifosi, but not the cheapest way into it if you are price conscious.

The general picture is that there's a lot of demand for bikes under £1,000, so make sure whatever you get interested in can actually be supplied in a reasonable time. 
Your shop will also have asked you what you want to use it for, where it will be parked, when/where you plan to ride it (Peaks, Fens; rain - mudguards) what if anything do you need or want to carry on it.

I don't run any disc brakes and never have on a road bike. Your main enemies as a bike buyer are complexity, weight and expense - in my view discs give you all three, with little benefit unless you're fully laden in the hills in the rain. It's not obvious if it can take proper mudguards. 

I'm not sure if the Tifosi I can see linked below runs any of the new-fangled bottom bracket bearings: traditional threaded aren't perfect, but the new standards aren't  providing any fresh benefits.  I don't know how well the FSA cranks perform, but This is a compromise - I'd recommend sticking to an all-Shimano spec. 

https://www.fawkes-cycles.co.uk/2498028/products/tifosi-scalare-disc-tia...

I can't see any pedals offered here - just to note for budget purposes. If you go for carbon, treat it with respect. Your money will go further with an alu or steel frame. The model above offers a decent range of gears, which I'd expect at entry level.
 

good luck! 

You don't have to budget £1500 for a new bike, but under the present C19 conditions and that you've started your search at your local bike shop, which I think is commendable by the way, you do limit yourself to what they have in stock. The boom in bike buying during the pandemic has certainly limited the choice, so if you are happy meeting that price point the Tifosi is well reviewed and if the bike is actually available then even better. 

If I was looking for other bikes in that price bracket I'd personally look at the Ribble CGR AL or a Canyon Endurace AL, both of which are aluminium framed rather than carbon and are online sales rather than direct from a shop.

Perhaps the biggest question that you don't answer is your intentions for the bike. Is it going to be a commuter? Something to do a couple of longer rides a week etc. It's very easy to get carried away witha new purchase without actually considering the practicalities of why and what you intend to do on the bike.

£1500 is a cracking price point and the vast majority of bikes you'll find available at that price bracekt will meet your needs, but having the option of mudguard mounts or the ability to fix a rack to the frame increase it's potential to be more than just a summer bike.

These are the questions I'd be asking myself when trying to decide what I wanted.

Are you doing it via the cycle to work scheme or self funding?