Hi Ross and welcome to the forum.
As Big Ada says if you don't have time to build or want something to put on the water ASAP then see the classifieds in Model Boats or Marine Modelling International magazines or local clubs.
However, if you do want to build a kit of a cruiser than I suggest the following:
For early cruisers (approx 1m long) go for Deans Marine
Either SMS Emden (German light cruiser WW1)
HMS Scout/Skirmisher (late Victorian cruisers)
HMS Dido (WW2 Anti aircraft cruiser) big bigger closer to 4-5ft long
All are to 1/96 scale (the most common warship scale)
For later cruisers go for Fleetscale
They do a variety including County class, Town class, Dido class, Colony class, and a few other nations including Takao and Prinz Eugen in the smaller scale of 1/128.
In 1/96 scale they do Dido class, town class and modified Leander class. All WW2.
Remember though... They aren't like Airfix kits and require some work by the modeller to use the plans to make the superstructures. There are very few kits out there that are like their aircraft or tank cousins which don't cost a small fortune.
Radio gear is usually extra and not usually included in the price of a standard kit but these days you can pick up a decent 2.4GHz transmitter and receiver for less than £60.
All the hulls in these kits are made from Fibreglass, unless you want to convert a plastic kit from Trumpeter or Tamiya you won't find a plastic hull or ABS hull readily available in the UK.
Every kit will have a fittings pack to detail the model but it's entirely up to you how far you go and are happy with.
I like cruisers particularity Royal Navy but I do have a Emden in 1/96 scale. I have a Ceres class Anti aircraft cruiser (built using a Deans Marine hull and fittings) in 1/96 and I intend to have a 1/96 County class cruiser and an a Italian protected cruiser in the future but they will be scratch built.
Hope this helps and if in doubt ask we all here to help