I like staying around the LK Metro area, plenty of places for food nearby including the 24 hour kiss restaurant on 2nd road at the end of soi Diana. The beer bar complex on Diana is good for a drink or two until the wee small hours as well.
LK metro is worth a look for the gogo's and bars alone, but you are also situated about half way between walking street and soi6, daytime places like devils den, lolitas, club exyte and the new telephone bar are all either in or 5 mins walk from LK.
Ive stayed in the guesthouses like Billabong and The Irish Rovers on LK metro which are all sub 20 quid a night, but you wont get much sleep until after 3 or 4am, the rooms are generally big if you dont go for the basic ones and clean, the bed might've seen better days, but they are often the rock hard types that thais seem to favour (and i quite like), and dont expect a nice flat screen either. But to be honest unless you pick up a dose of the shits who is going to be spending much time in the room anyway.
Occasionally ive paid more for rooms in hotels that claim to have seaviews, but there are so many rooms with shit seaviews and shit balcony's ive kinda given up on this.
recently ive stayed on soi honey at the 24/7 boutique hotel, its a new hotel, has a roof pool and gym and you can get it for around 23 quid a night often with breakie included, which isnt bad, the rooms are nice and modern including flat screen tv and swan shaped towel arrangements. The bathroom has windows that look over the bed, so if your barfine is shy you can watch her shower from the bed, well until she notices the blinds that can be closed for privacy

Soi honey has the 24 hour massage places where you can get full service first thing in the morning, it also has a decent pharmacy that wont try and rip you off and there is the soapy the soi is named after but ive never tried it.