The de-facto standard of PMR radios is the Kenwood TK3201, solidly built, military standard, robust and reliable. Used ones tend to sell on eBay for around the £50-60 mark so should be around your budget.
The alternative is a pair of Puxing PX888s; these are Far East built and available from Hong Kong via eBay and directly from a few suppliers over there. They are solid, decent radios all things considered. However, these do not comply with OFCOM regs for PMR so are technically illegal in the UK. Namely: They have the ability to transmit outside of the PMR 446.00625 MHz to 446.09375 MHz frequency range, transmit at 4W (OFCOM regs say 0.5W) and have a detachable antenna. The last point is a bit of a grey area as you can legally modify an approved radio to take an external antenna so long as the resulting transmitted power still doesn't exceed 0.5W ERP.
PX888s are about £45 delivered. The PX888 uses the Kenwood accessory socket so it can be connected to intercoms and headsets interchangeably using the same leads.
Don't be fooled into thinking that 4W vs. 0.5W will mean eight times the range for the more powerful set. As well as the inverse square law there are many other factors that mean you will get more, just not as much as you think...
The enforcement of what kit you have shouldn't really be an issue on a bike as you're a moving target and are not going to be a nuisance (i.e. washing out the signal of other PMR users) for very long. If you were, for example, running security for a night club or using them on a building site then there might be a complaint that would lead to an investigation as you would be transmitting from one location for days on end. On a bike you're usually out of range and not an issue within minutes or less.
If you don't have intercoms or suitable headsets then your budget is woefully inadequate I'm sorry to say. You need proper noise cancelling mics otherwise you're going to be very frustrated with the results over 30-40mph. Best entry point would be an Autocom Active Rider Plus, these can be had for around £30-40 off eBay though you would need a few cables for an effective set-up. I would budget around £60-70 for each excluding the radio.
An alternative is the
McKay headset, though unlike the Autocom adding other inputs isn't an option. The open face version has a good noise cancelling mic and works in all full face helmets I've tried. This has a PTT button included. PTT is vital, VOX just doesn't work on a bike unless you're using the VOX built into the likes of an Autocom unit, even so PPT is far better.
Also, locating a radio on a bike can be problematic, lie one down with the integral antenna and the range will be drastically compromised.
An external antenna kit works really well but will run you another £45 odd. It really starts to add up.
I would say that your cheapest effective option would be a pair of Puxings, a pair of McKay headsets and a couple of bum bags with the radios upright, antenna poking out of the zipper. That would, I'm afraid, come to more like £100 each set-up.
Whatever you do don't go for the cheap Maplin/Argos hobby type radios and Maplin's so called M/C headset (or similar ones off eBay), they'll wind up in the bin after a few frustrating rides.
