If you're up for DIY, roasting your own is surprisingly easy and potentially a very cost-effective way to get awesome results. Fresh coffee trumps old coffee any day of the week. Many people start noticing a degradation in flavor of roasted beans after 10-14 days. So by roasting your own, you should easily be able to enjoy maximum flavor and minimum price. As for the "nutty" flavor you like, that has a lot to do with the region your coffee comes from. You might try Brazilian and other South American coffees. The "muddy, bland" flavors are hallmarks of old beans. Me personally, I dig the fruity/floral flavors of Ethiopian coffees. But discovering these differences (and the impact of how dark you take your roast) is part of what makes home roasting such a fun learning endeavor.
Fair warning - all of the names I'm about to drop are from the U.S., so you might need to scour the internet a bit to find comparable alternatives in the UK.
The easiest way to start roasting your own is with an old popcorn popper. The Poppery is an air popcorn popper that works well. Here, they can be found at thrift stores for $5-$10. Do a little research online to find what other home roasters in the UK are using, because not all popcorn poppers work well for coffee. Next, you need to find a resource for green coffee beans - in the U.S., Sweet Maria's is a great resource for online purchases. Green coffee beans will run about $6 per 16oz (most "fancy" coffee bags are actually just 12oz). So there you go - for as little as $15, you can be up and running and your ongoing expense can be as little as $6 per pound/16 oz (if anyone is really scrutinizing the $/ounce, also factor in about 15% weight loss during roasting).
As for technique - turn the popper on, pour in beans until the air is no longer rapidly spinning them around the roasting chamber (but they should definitely still be moving a bit). After some minutes (I think it was about 7 minutes on my Poppery), they will be starting to look brown and you will hear "first crack". Sounds a bit like popcorn popping. This is the first point you might decide to pour them out to cool - corresponds to a rather light roast. If you leave them in long enough, they will go quiet, and then later enter "second crack" and the process gets noticeably more smokey (you will want to roast outdoors). This is about the darkest you are likely to want to take them.
Anyway, that's about all there is to it at first. Super easy, super fun, great opportunity to get to know your food a little more deeply and save money in the process. If you decide you like roasting , you will probably next get a nicer roaster that can do larger batches because the popcorn popper will probably only do one or two day's worth at a time. I think the Behmor 1600 is currently the sweet spot for price relative to batch capacity. It will roast about a pound at a time.
Enjoy!