Agree with Cypher - Both cages are far too small for any size of hamster. It's a shame that pet shops sell them. Apologies if you like it but the Pico cage is horrible! Totally unsuitable for a hamster as it's too small, too high and has fall risks. RSPCA minimum recommended size is approx 80cm by 50cm continuous floorspace (ie in one cage). So if one of your cages meets that, then an add-on cage could be a bonus, but really you'd be better with one larger cage.
I've just upgraded our hamster from an 80cm cage to the 100cm Barney cage - the Barney is really good value at less than £50 and it comes with most of what you would need. It has a good sized house, a shelf and a ladder. Even the wheel isn't bad for a temporary measure - it's about an 8" wheel - which would be ok for a dwarf hamster but a Syrian would need something bigger/sturdier quite soon.
This is the Barney cage at Zooplus, as Cypher mentioned. It might not look so much fun but it can be made to look fun quite easily with a few toys (home-made or otherwise) and you'd have a very happy hamster in there.
Barney Pet Cage | Great deals at zooplus!
The Alexander is also a great cage and comes with everything you'd need except a wheel - it has 3 houses (although one has a window that's small and needs taking out or the window blocking off) - but it costs a bit more.
Great deals on small pet cages at zooplus: Alexander Small Pet Cage
Both of those cages have narrow 7mm bar spacing so are quite futureproof as suitable for either a Syrian or a Dwarf hamster. Both species need a lot of floor space as they are very active creatures.
The Alaska is about the smallest size suitable - and is only £33 but could do with a house (the white one on the shelf isn't really suitable for a Syrian as the holes are too small) so that reduces it's value for money a bit, when the Barney comes with a good house and shelf. It has 1cm bar spacing so would be more suited to a Syrian than a dwarf hamster.
Alaska Hamster Cage | Free P&P on orders £29+ at zooplus!
How long have you had the pets at home cage? Some people have been successful in taking them back for a refund, even after they have been used, if they haven't had them very long. That way you could afford more
I noticed on the description of the large pets at home cage it says it is suitable for one syrian hamster. Which it isn't - so someone should tell them that I reckon!
Not sure if you have a Syrian or a dwarf hamster, but Syrians also need an 11" to 12" wheel - which won't fit in small cages really. Most cages, even the larger ones, only come with a small 6" wheel as standard, which is ok for a dwarf hamster (just) but not for a Syrian.
We can recommend wheels if you like, when you've decided on a cage. The cheapest suitable one is about £9 I think.
The Hamster Heaven is also popular and meets RSPCA minimum recommended standards, but I reckon the Barney and Alaska are better value. Most people end up taking out the tubes and penthouse as hammies tend to block tubes up and pee in them, and they are an escape risk. People usually end up removing at least one of the shelves to fit a syrian sized wheel in, plus the ladder breaks sometimes. But it's a well made cage with a nice big front opening door. Our hamster grew quite large and was too big for those kind of tubes, so hammies are better with larger rat, sized floor tubes really. But there are people who are happy using the tubes and penthouse if their hammy isn't too big.
Hamster Cages: great selection at zooplus: Hamster Heaven 80 Cage