I have the choice of a
- 2-man Vaude tent,
- 8-man polycotton Bison tipi,
- Hennessey Hammock
- UKHammocks Woodsman hammock
- two Hex hammock tarps
- one 2x3 sil nylon tarp
- one 3x4 urethane/nylon True North tarp
- a home sewn breathable bivi bag (does not zip closed)
I am a huge fan of hammocks and tarps, but find that they are rather specialized and far from a good universal sleeping arrangement. I have found them excellent in southern Sweden and Norway (April to September for my trips). They fall down (pun intended) in most official camp sites due to the general lack of suitable support trees. For wild camping in the UK they aren't great either because permitted wild camping is mostly on moors, again not many trees. Even for non-permitted stealth camping (which we can't condone) they aren't great because of needing trees of a suitable size and spacing, and they can take up a fair foot print size.
A 2x3 tarp is a bit small for use with a hammock, but offers enough dry space when pitched lower and used for a ground sleeper. The down sides are the lack of bug protection; ticks, harvest mites, slugs, beetles, midges and mossies, and that you very limited privacy when using camping fields/official sites. A bigger tarp, 3x3 and up, can give you a bit more privacy, if you pitch it right, but still not full 360deg the way a tent does. Tarp's big benefit is in how they can be ventilated, which you lose if you pitch low to the ground in a grass field. In that case the condensation and subsequent tarp-sag can be enormous.
If you are looking for the most versatile solution, a tarp and bivi can be used together, or separately, and the tarp can be set up next to a tent to give you a nice food prep/eating/sitting area. The tarp can be used for a hammock, purchased later if you want.
Not knowing what sort of 2-man tent you have, I wouldn't want to advise you stay with it, but tents are good choices for a lot of things in the UK. The challenge is getting one that is light enough not to be a burden without breaking the bank.