I don't know your budget but given you're tempted by dirt cheap tires i'm tempted to say you don't want to fork out too much.
And given your specific criteria (Road but Mostly Off-road capable, light & sporty) that narrows your choices down.
Well before we dig into that, the tires you're looking at (ultrasport 2) are slick tires.
That implies they're made for Road use. Which typically means softer rubber, which doesn't handle Cuts or Grazes very well.
the soft rubber will give you alot of good grip (on clean tarmac) and speed, but will not do near as good off-road.
You're going to want to find something with a bit more of a "tread" pattern. But not 'knobbly' tires per-se. You want to balance a combination of Aggressive off-road 'knobbly' tread and Softer road-focused 'slick' tread. -- Something that'll bite into dirt, mud, stones, but not get cut to pieces by such those things.
The right tread design will help give you good grip off-road and minimize cuts that might otherwise be fatal to your tire.
Back to your criteria.. Looking for your tire will show us that you don't often find that kind of off-road capable tire for your size of 25-28c.
The reason being, most off-road tires come with much higher air volume (bigger size) so we're talking more 32-38c
But, there are some exceptions. But even fewer exceptions when we add in your requirements of something Fast and Light.
So, here's my top picks for you.
1) Vittoria Zaffiro 700-28c < This is the best VFM Option with some places selling them at £4.99 (special sale) each. While those low prices
may indicate poor quality, the truth is they're the lightest weight option & have incredibly robust rubber and they are-
-good on tarmac. They weren't initially designed for off-roading but have the majority of criteria for such action - that said however they
won't be all that happy in Mud due to their rather shallow tread design but will find comfort on rocks, gravel and road.
2) Vittoria Randonneur 700-28 < This is more expensive (£12.00-16.00) but more off-road focused than the zaffiros.
But the flip side is, because it caters more for off-roading than the zaffiro it is generally heavier than the zaffiro; but the very minor speed penalty is made up with with more off-road ability, grip and control. They are also welcome on the road as well.
Now thinking of it here I would of given you more options. From other brands, such as Continental and Schawble.
But the majority I find are Heavy & Slow and I wouldn't recommend them for your needs. They're not Quality, Cheap, Light and good at performing off-road.
Others may give you alternative options - but I urge you to investigate further with the Zaffiro & Randonneur if you're feeling like spending more money they do "pro" versions of each of those tires. - Keep in mind I chose those two for you out of my experience with Vittoria brand and my needs for an off-road / road capable tire, there are other options but I wouldn't recommend those to you.
-- But if all else doesn't please you, you'd discover an entire new world of tires that would suit your needs if you upgraded your tire size to something around 32-38c and if you did that I could give you a list of suitable tires ranging from 1-9 rather than 1-2. Which, if you're off-roading alot I would MORE than recommend.
Just make sure your bike can take that tire size however.
