Dripping tap in kitchen

I would generally agree with your plumber, it’s difficult to source the correct cartridges and can be equally time consuming and costly as replacing a new tap. So may as well get a new tap

No will need to check wether I can change the cartridge or washer

Some cartridge taps have no spares readily available however many different types of cartridges are used by different manufacturers and personally sourcing correct type is time wasting and expensive.Changing complete tap is often the best and quickest option If tap is five years or older change it !

If its quarter turn ceramic disks, it’s better and cheaper to change the whole tap ,than mess around trying to source the correct inserts of which there’s thousands of different types if inserts.

There is no straightforward answer to this without examining the tap in question. What I can say though is that many taps can be fixed, but some more easily than others. Fixing a dripping tap nowadays is often not such a simple task as replacing a washer like it was years ago. In fact perhaps the biggest proportion of kitchen taps particularly, do not have washers at all but a ceramic disc cartridge of which there are many different types. These need to be identified in the first place before a repair can take place. Some if available can be extremely expensive, others as cheap as chips by comparison. The next thing to consider is the general condition of the tap. Is it leaking from the base of the spout ? If so, again it depends upon the construction & brand as to whether it is viable, or indeed if seals can be obtained. The O rings are often an intermediary size & if not exactly right will either not fit or be too slack, finding the right seals from a generic selection is usually unfruitfull. With some of these taps, there is sometimes a chance that generic parts will fit, or that a generic valve & head repair kit could be used. Different valves have different external dimensions, shaft length, diameter & spline types. If these do not match then the old heads wont fit. Valve & head repair kits can cost £20 - £30. You don't know if they will fit till you get the old ones out,, if you can. So for all the above reasons, as well as many other considerations, it is sometimes a better choice to fit a new tap, particularly if accessibility is good & the job is straightforward. On other occasions it may be better to go to the ends of the earth in an attempt to find the right parts. Last year I had a very good example of this. I knew what the tap brand was & it required new ceramic discs which were special ones & not a regular pattern & in the first instance likely to be expensive, if indeed still available. The kitchen was about 20 years old & in a very good state of repair, finished to a high standard. However in order to get at the tap base & pipework, the back of the cupboard would need cutting away to begin with, so replacement was far less of an option as was hoped. Upon investigation I found the spares were now obsolete, however there were a limited quantity of pattern spares available at a cost of around £80. In this case a repair was carried out, where normally I would have replaced the tap. It was an expensive repair, given the time involved, cost of parts etc, which would not normally be viable. So, it is very much the individual circumstances which determine the best course of action. Having said this, I do specialise in repairs & have donkeys years of experience. Many guys nowadays don't & will seek to replace as a matter of course. The moral of the story is to choose your plumber wisely. I hope this has helped.