Integrated appliances are typically universal and DIY Kitchens has standardised sizes; any single oven will fit in either a built-under or eye-level oven housing.
If you're looking at a built-in oven/microwave combination, be aware that microwaves can be ~380 (Built in Microwave) or ~450 (Combination Built in Microwave) so the type of housing you need may change.
If you're looking at a double oven; check the size. Most are standard at ~900, but a rare few are ~1000+. Also be sure that you're looking at Built-IN double ovens if you want it eye-level.
Built-UNDER double ovens don't take a housing and go under the worktops.
If you're putting a built-in microwave into a wall unit, not a tall housing .. check the depth of the unit and the microwave. Some appliances are too deep for wall units.
Integrated dishwashers come in standard (60cm) and slimline (45cm) sizes.
On the sink & taps, check the size of the bowl(s) is smaller than the cabinet that you're putting it above. Most conventional sinks will require a minimum of a 500mm-600mm cabinet underneath it, but there are exceptions.
On Hobs, consider the drop; especially if you're looking at induction hobs. They're deeper than most worktops (especially thin worktops like 20mm quartz or 12mm compact laminate) and will need a cabinet underneath them that won't obstruct the hob.
As long as the cabinet is the same size/larger than the hob, you should be fine. Just don't (for example) put a 500mm unit under a 600mm induction hob with 12mm worktops.
Integrated Fridge/Freezers are typically 50/50 or 70/30, and housings are the same; just a case of matching them.
Extractors can be tricky. If you're using colour-matched clad on panels on the wall units, be sure to bear in mind that they'll reduce the space you have available for your extractor.