Under unit kitchen and ceiling spot bulbs keep blowing.

If these works were carried out between 2005 and 2013 then you should have the minor works certificate as a minimum and compliance certificate showing the work has been registered as required by building regs. This as a minimum would indicate works were carried out by someone qualified i.e knows what they are doing. If installation has been carried out correctly the reason is probably a mix of using cheap lamps to replace the blown lamps and they are probably 12v halogen lamps which do run incredibly hot so do burn out quite regularly. I would recommend replacing with LED lamps which run virtually cool and will last on average 25,000 hrs against 2,000hrs on the lamps you are currently using.

Yes, cheap chinese made bulbs and also your probably not wearing gloves when you replace them. The glass part of the bulbs must not be touched by your hands/skin when inserting them as you leave residues of natural oils from your skin on the surface of the bulb which makes them fail very quickly. If possible invest in LED bulbs (approx. £7 each), and they should last for years.

Probably a loose joint somewhere or overheated fittings. I would convert to led where possible.

If your under unit light fittings are low voltage and hence use G4 lamps then you cannot touch the lamp with your bare fingers when replacing them. This will cause the lamps to fail prematurely almost everytime. The same can be said of G9 mains voltage lamps. With regards to your down lights, low voltage halogen down lights often fail as a result of a worn out or burnt lamp holder. A faulty transformer can also be a cause, loose terminations can also have an Impact on lamp life. Mains voltage halogen down lights can also fail prematurely for a variety of reasons. It would be worth getting a Part P registered electrician to call out and do a quick assessment of your existing arrangement to identify any potential underlying issues. Converting to LED could be a good option for you if the circuit as a whole and the existing terminations are currently done to a proper standard.