Hi and Welcome. We don't see much hornby here but I did review their website.
First point is, do you want steam or diesel.
Are you interested in DCC? The starter set was expensve but you get two engines and a DCC set up. DCC simply has more bells and whistles, and allows multiple engine use. I would say it is worth the price. Two sets looked good, the western and eastern. If you look at separate engine prices DCC ready are more. In running multple trains, DCC gives command directly to the engine, with transformers you control the speed on what section of track the engine is located.
Also important is the area you have. If it is small you may not want to get the DCC . I think the passenger sets are nice runners when lighted.
Being an adult, the DCC may suit you in the long run.
The little blue diesel looked nice but it was out of stock.So recap.
Price ,style, area, and controller(DCC or conventional).