Is dell XPS desktop good

For a prebuilt system, its about the best you're gonna get. You're gonna pay around that amount from any of the big PC manufacturers for a computer with those specs. You could definitely save money if you could live with a lower model video card.

@kuweihang  - You said  it has 12th Gen CPU, so it's probably an XPS 8950.

You also said 2500£ (Sterling) so you must be in UK, which puts the price above ~US$3000, so it is an expensive PC.

The XPS 8960 with a 13th Gen Intel CPU seems to be on it's way, so prices for the XPS 8950 could start dropping. No idea when the XPS 8960 will be available in US or UK, but if you can hold out a while, maybe you might get a better price on an XPS 8950, or possibly get an XPS 8960 with its 13th Gen CPU for similar price to what you'd pay today for the XPS 8950 described above.

Obviously, this is entirely your decision since I have no idea what the pricing and availability for XPS 8960 will be in UK, or possible impact on XPS 8950 prices, and how urgent your need is...

I would do like @RoHe  suggests, wait for the XPS with the 13th gen CPU. My XPS 8950 is 13 months old and It has a 12700k, 32 G RAM, rtx3060Ti, liquid cooling and 750 W PSU, 1TB NVMe and a 1TB HDD. It cost me $2500 USD.....over a year ago.

Sorry, had the wrong currency

2,500 British Pounds

3,077 U.S. Dollars

Is dell XPS desktop good

Just like beauty is in the eye of the beholder, the XPS (8950) is good only to its user.  While the consensus from ten of thousands of non-reviews XPS owners implied that it's a good product, several dozens have described their displease with the 8950 through bad reviews and some have had posting in this community as well.

Even if they're not that accurate, people may see negative reviews as more informative because they share the deficiencies of a product.  What these posts had in common were a bad product that did not meet the expectation (top of the line performance) of a premium investment purchases.  Adding to horrid experiences and useless services from Pro support.  It paints such a mediocre product that would influence decision making of pre-purchasers. 

On the contrary, after reading those negative postings, from my perspective, I conclude that the XPS 8950 is a very good product.  In fact, it's too good that despite all the problems and issues right out of the box and despite all the pains and the agony users have gone through with warranty support, many of those XPS owners decided to keep their machines at the end, in stead of returning them.

Is this worth 2500£.

At premium price, the XPS has a better profit margin than those of entry level and budget models.  But it could quickly diminishes due to high demand of system (motherboard) exchanges and in-home warranty services.  After adjustment and offset, I would consider it's a fair market price.

I bought this top-notch XPS8950 on the first day it released. Surprisingly after 14 months the price still holds. My previous desktop purchasing experience was 17 years ago for (if I remember correctly) Dimension 9100. Overall the experience is good.  I have upgraded to 64G Crucial DDR5, added 1 x WD sn850 2T NVME SSD, 2 x Crucial MX500 2T 2.5 inch SSD and 1 x WD 18T 3.5 inch HDD along the way. Everything works as it should. Only one "service" call to DELL misled me to end up getting a WD Black 2T 3.5 inch HDD (as the rep warns me anything larger than 2T is in-compatible)  which cost me half of the price for the 18T.

Briefly reviewing the exploded view at https://www.dell.com/support/manuals/en-us/xps-8950-desktop/xps-8950-service-manual/major-components-of-xps-8950?guid=guid-49c2be82-aed0-49c9-a7d7-c88dee2456b1&lang=en-us , it appears the xps 8950 is not standard in any way other than cpu, ram and storage.

The core components including case, power supply and motherboard are NOT standard. Also probably some oem version of the video card.

As someone who fixes pc's, proprietary parts just makes things more complicated (and expensive). Assuming you know what you're doing or know someone that does, building a pc from standard parts isn't all that complicated.  So yes, you can do better.  Not to mention, dell's motherboard bios are very limited in what options are exposed. Great for the layperson, terrible for the tweaker.

Personally, I'm a fan of asus motherboard over others. Sure they're all standard, but i've had the best experience with them over the last 2 decades.