Your answer depends on what your objectives are: going zero carbon, capability of operating in "island" mode off grid for a short while, or just reducing your energy bills a bit. Quick thoughts (happy to expand or take up conversation via PM)
Firstly - invest in energy efficiency. This is almost always the cheapest way of reducing your bills. LED lights, A++ rated appliances, timer controls, etc. Worth investing £20 in a plug in power monitor so you can see how much juice your appliances actually use. It's enlightening - see July edition of The Energyst magazine, pages 50-51, for my article on the subject (although note the bloody editor dropped a zero off one of the numbers in Figure 2
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https://theenergyst.com/the-energyst-magazine-latest-edition/ * Micro CHP - unlikely to be useful. Various different technologies have been tried, including stirling engines, and there may be some still available. However, the basic premise is that you can do something with the heat being generated in order to keep them running long enough to offset a good chunk of your electricity demand. This may suggest you'd want a decent size thermal store to allow the CHP to run-on a bit and stop it cycling on an off. It may be worthwhile if you have a hot tub you want to drop waste heat into. Generally, the technology is complex - there are few of them about, and long-term servicing availability may be tricky.
* Heat pumps. These fall into various types. Ground source (GSHP) are likely to work out very pricey for most folk due to the need to install ground loops or a borehole (or 2). Air source (ASHP) though are within the realms of possibility, and the new 3rd generation systems can operate fairly efficiently at higher output temperatures. Nonetheless, they do work far more efficiently at lower output temperatures and are better suited to properties where you have underfloor heating and where the property isn't ancient and leaks heat all over the place. You can get hybrid heat pumps which work alongside a small gas or oil boiler, so the heat pump does the baseload low temperature stuff using grid electricity (which is become less carbon intensive rapidly), and then top up with the conventional boiler for peak load work. It adds complexity and space requirements to the installation.
ASHP/GSHP attract domestic renewable heat incentive (RHI) payments for 7 years for the renewable part of the load - up to a capped limit, but for the right property you could get a good chunk of your investment back. Additionally, the RHI rules now allow you to re-assign your RHI payments to a 3rd party, so there are folk out there who will part of fully fund your installation and bank your RHI payments which alleviates the up-front capital strain. Requirements include that both the kit and the installer are accredited by the Microgeneration Certification Scheme.
Solar PV - for a flat roof or east/west orientation expect to lose 10-15% of optimal generation, but you should still yield perhaps 800 - 900 kWh per kW peak generation sizing per annum (e.g. 4kW array x 800 = 3200 kWh/year), of which you'll probably use 35 - 50% on site and spill the rest to grid. There are some great smart controls out there which work to utilise your generation on site (e.g. by switching on/off your immersion heater, or an EV charger) to avoid spilling to grid. (see myenergi.com for examples). PV would be ideal if you also have a heat pump (although peak PV generation is in the summer/peak heat pump electrical demand is in the winter) or if you have an electric vehicle to charge. Expect the inverter to need replacing any time after about 7-10 years, but the panels should be good for 25+ with some performance degradation over time.
Solar thermal (hot water). Can contribute 100% of domestic hot water even on not particularly sunny days, but payback is fairly long - especially if you currently have gas heating. I have solar thermal, controlled to work alongside my wood pellet boiler, and it does a great job reducing the summer demand on the boiler, and still makes a contribution on sunny winter days. Not sure if solar thermal still attracts domestic RHI payments. I know I'm getting RHI for mine but it was installed 5 years ago.
There are other technologies out there too. Forget small wind power. It only gets economic on sites with clear wind flow (i.e. not right next to a house!) and at larger scale (say 15kW and up), so best suited to farms and the such like.
DON'T FORGET SERVICING COSTS!
A typical gas/oil boiler costs around £50-100 to service each year depending on location and whether or not your engineer is VAT registered. My wood pellet boiler costs £380 a year to service! Heat pump service prices are currently in the realm of £300 including VAT per year although you can probably get away with servicing less frequently (although should still have pressure vessels safety checked). Any RHI payments help offset these costs for the 7 years but once the RHI stops paying out you could be left with increased service costs. I think heat pump servicing costs will drop very rapidly once the RHI gets canned and once the forthcoming ban on new installations of fossil fueled boilers comes into play in a few years.
Hope that helps. Others OTP should have further insight. Paging Mr Woofage....